Refactor HeaderField and HeaderName constructors for efficiency

Remove unnecessary object creation in HeaderField copy constructor. Simplify HeaderName by removing redundant copy constructor.

core/src/main/java/com/predic8/membrane/core/http/HeaderField.java

@@ -45,9 +45,10 @@ public HeaderField(String headerName,String value) {
 	}
 
 	public HeaderField(HeaderField element) {
-		headerName = new HeaderName(element.headerName);
+		headerName = element.headerName;
 		value = element.value;
 	}
+
 	public String getValue() {
 		return value;
 	}

core/src/main/java/com/predic8/membrane/core/http/HeaderName.java

@@ -29,10 +29,6 @@ public HeaderName(String name) {
 		this.name = name;
 	}
 
-	public HeaderName(HeaderName hn) {
-		this.name = hn.name;
-	}
-
 	@Override
 	public boolean equals(Object obj) {
 		return (this == obj) || (obj instanceof HeaderName hn) && (name.equalsIgnoreCase((hn.name)));