Add remaining missing .NET 9 docs for System.Collections (#10520)

* Add remaining missing .NET 9 docs for System.Collections

* Apply suggestions from code review

Co-authored-by: Genevieve Warren <24882762+gewarren@users.noreply.github.com>

---------

Co-authored-by: Genevieve Warren <24882762+gewarren@users.noreply.github.com>

xml/System.Collections.Concurrent/ConcurrentDictionary`2+AlternateLookup`1.xml

@@ -32,6 +32,8 @@
     </Attribute>
   </Attributes>
   <Docs>
+    <typeparam name="TKey">The type of the keys in the dictionary.</typeparam>
+    <typeparam name="TValue">The type of the values in the dictionary.</typeparam>
     <typeparam name="TAlternateKey">The alternate type of a key for performing lookups.</typeparam>
     <summary>
       <para>Provides a type that may be used to perform operations on a <see cref="T:System.Collections.Concurrent.ConcurrentDictionary`2" /></para>

xml/System.Collections.Frozen/FrozenDictionary`2+AlternateLookup`1.xml

@@ -36,6 +36,8 @@
     </Attribute>
   </Attributes>
   <Docs>
+    <typeparam name="TKey">The type of the keys in the dictionary.</typeparam>
+    <typeparam name="TValue">The type of the values in the dictionary.</typeparam>
     <typeparam name="TAlternateKey">The alternate type of a key for performing lookups.</typeparam>
     <summary>
       <para>Provides a type that may be used to perform operations on a <see cref="T:System.Collections.Frozen.FrozenDictionary`2" /></para>

xml/System.Collections.Frozen/FrozenSet`1+AlternateLookup`1.xml

@@ -42,6 +42,7 @@
     </Attribute>
   </Attributes>
   <Docs>
+    <typeparam name="T">The type of the values in this set.</typeparam>
     <typeparam name="TAlternate">The alternate type of a key for performing lookups.</typeparam>
     <summary>
       <para>Provides a type that may be used to perform operations on a <see cref="T:System.Collections.Frozen.FrozenSet`1" /></para>

xml/System.Collections.Generic/Dictionary`2+AlternateLookup`1.xml

@@ -32,6 +32,8 @@
     </Attribute>
   </Attributes>
   <Docs>
+    <typeparam name="TKey">The type of the keys in the dictionary.</typeparam>
+    <typeparam name="TValue">The type of the values in the dictionary.</typeparam>
     <typeparam name="TAlternateKey">The alternate type of a key for performing lookups.</typeparam>
     <summary>Provides a type that can be used to perform operations on a <see cref="T:System.Collections.Generic.Dictionary`2" /> using a <typeparamref name="TAlternateKey" /> as a key instead of a <typeparamref name="TKey" />.</summary>
     <remarks>To be added.</remarks>
@@ -227,7 +229,7 @@
         <param name="key">The alternate key of the value to get.</param>
         <param name="value">When this method returns, contains the value associated with the specified key, if the key is found; otherwise, the default value for the type of the value parameter.</param>
         <summary>Gets the value associated with the specified alternate key.</summary>
-        <returns>To be added.</returns>
+        <returns><see langword="true"/> if an entry was found; otherwise, <see langword="false"/>.</returns>
         <remarks>To be added.</remarks>
         <exception cref="T:System.ArgumentNullException">
           <paramref name="key" /> is <see langword="null" />.</exception>
@@ -258,7 +260,7 @@
         <param name="actualKey">When this method returns, contains the actual key associated with the alternate key, if the key is found; otherwise, the default value for the type of the key parameter.</param>
         <param name="value">When this method returns, contains the value associated with the specified key, if the key is found; otherwise, the default value for the type of the value parameter.</param>
         <summary>Gets the value associated with the specified alternate key.</summary>
-        <returns>To be added.</returns>
+        <returns><see langword="true"/> if an entry was found; otherwise, <see langword="false"/>.</returns>
         <remarks>To be added.</remarks>
         <exception cref="T:System.ArgumentNullException">
           <paramref name="key" /> is <see langword="null" />.</exception>

xml/System.Collections.Generic/Dictionary`2.xml

@@ -1302,10 +1302,11 @@
       </TypeParameters>
       <Parameters />
       <Docs>
-        <typeparam name="TAlternateKey">To be added.</typeparam>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
-        <remarks>To be added.</remarks>
+        <typeparam name="TAlternateKey">The alternate type of a key for performing lookups.</typeparam>
+        <summary>Gets an instance of a type that can be used to perform operations on the current <see cref="T:System.Collections.Generic.Dictionary`2"/> using a <typeparamref name="TAlternateKey"/> as a key instead of a <typeparamref name="TKey"/>.</summary>
+        <returns>The created lookup instance.</returns>
+        <remarks>The dictionary must use a comparer that implements <see cref="T:System.Collections.Generic.IAlternateEqualityComparer`2"/> with <typeparamref name="TAlternateKey"/> and <typeparamref name="TKey"/>. If it doesn't, an exception is thrown.</remarks>
+        <exception cref="T:System.InvalidOperationException">The dictionary's comparer is not compatible with <typeparamref name="TAlternateKey"/>.</exception>
       </Docs>
     </Member>
     <Member MemberName="GetEnumerator">
@@ -3410,11 +3411,11 @@ Unlike the <xref:System.Collections.Generic.Dictionary%602.Add%2A> method, this
         </Parameter>
       </Parameters>
       <Docs>
-        <typeparam name="TAlternateKey">To be added.</typeparam>
-        <param name="lookup">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
-        <remarks>To be added.</remarks>
+        <typeparam name="TAlternateKey">The alternate type of a key for performing lookups.</typeparam>
+        <param name="lookup">The created lookup instance when the method returns true, or a default instance that should not be used if the method returns false.</param>
+        <summary>Gets an instance of a type that can be used to perform operations on the current <see cref="T:System.Collections.Generic.Dictionary`2"/> using a <typeparamref name="TAlternateKey"/> as a key instead of a <typeparamref name="TKey"/>.</summary>
+        <returns><see langword="true" /> if a lookup could be created; otherwise, <see langword="false" />.</returns>
+        <remarks>The dictionary must use a comparer that implements <see cref="T:System.Collections.Generic.IAlternateEqualityComparer`2"/> with <typeparamref name="TAlternateKey"/> and <typeparamref name="TKey"/>. If it doesn't, the method returns <see langword="false" />.</remarks>
       </Docs>
     </Member>
     <Member MemberName="TryGetValue">

xml/System.Collections.Generic/HashSet`1+AlternateLookup`1.xml

@@ -31,6 +31,7 @@
     </Attribute>
   </Attributes>
   <Docs>
+    <typeparam name="T">The type of elements in the hash set.</typeparam>
     <typeparam name="TAlternate">The alternate type of instance for performing lookups.</typeparam>
     <summary>Provides a type that can be used to perform operations on a <see cref="T:System.Collections.Generic.HashSet`1" /> using a <typeparamref name="TAlternate" /> instead of a <typeparamref name="T" />.</summary>
     <remarks>To be added.</remarks>

xml/System.Collections.Generic/HashSet`1.xml

@@ -1309,10 +1309,10 @@ The following example demonstrates how to merge two disparate sets. This example
       </TypeParameters>
       <Parameters />
       <Docs>
-        <typeparam name="TAlternate">To be added.</typeparam>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
-        <remarks>To be added.</remarks>
+        <typeparam name="TAlternate">The alternate type of instance for performing lookups.</typeparam>
+        <summary>Gets an instance of a type that can be used to perform operations on the current <see cref="T:System.Collections.Generic.HashSet`1"/> using a <typeparamref name="TAlternate"/> instead of a <typeparamref name="T"/>.</summary>
+        <returns>The created lookup instance.</returns>
+        <remarks>The set must use a comparer that implements <see cref="T:System.Collections.Generic.IAlternateEqualityComparer`2"/> with <typeparamref name="TAlternate"/> and <typeparamref name="T"/>. If it doesn't, an exception is thrown.</remarks>
       </Docs>
     </Member>
     <Member MemberName="GetEnumerator">
@@ -2623,11 +2623,11 @@ The following example demonstrates how to merge two disparate sets. This example
         </Parameter>
       </Parameters>
       <Docs>
-        <typeparam name="TAlternate">To be added.</typeparam>
-        <param name="lookup">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
-        <remarks>To be added.</remarks>
+        <typeparam name="TAlternate">The alternate type of instance for performing lookups.</typeparam>
+        <param name="lookup">The created lookup instance when the method returns true, or a default instance that should not be used if the method returns false.</param>
+        <summary>Gets an instance of a type that can be used to perform operations on the current <see cref="T:System.Collections.Generic.HashSet`1"/> using a <typeparamref name="TAlternate"/> instead of a <typeparamref name="T"/>.</summary>
+        <returns><see langword="true" /> if a lookup could be created; otherwise, <see langword="false" />.</returns>
+        <remarks>The set must use a comparer that implements <see cref="T:System.Collections.Generic.IAlternateEqualityComparer`2"/> with <typeparamref name="TAlternate"/> and <typeparamref name="T"/>. If it doesn't, the method returns <see langword="false" />.</remarks>
       </Docs>
     </Member>
     <Member MemberName="TryGetValue">