fix[lang]: fix recursive interface imports (#4303)

fix a bug where imports inside of interfaces are not recursed into in
the import resolution pass. this is a regression in
6843e79.

tests/functional/syntax/test_interfaces.py

@@ -381,13 +381,22 @@ def test_interfaces_success(good_code):
 
 
 def test_imports_and_implements_within_interface(make_input_bundle):
-    interface_code = """
+    ibar_code = """
 @external
 def foobar():
     ...
 """
+    ifoo_code = """
+import bar
 
-    input_bundle = make_input_bundle({"foo.vyi": interface_code})
+implements: bar
+
+@external
+def foobar():
+    ...
+"""
+
+    input_bundle = make_input_bundle({"foo.vyi": ifoo_code, "bar.vyi": ibar_code})
 
     code = """
 import foo as Foo

vyper/semantics/analysis/imports.py

@@ -194,6 +194,7 @@ def _load_import_helper(
             file = self.input_bundle.load_file(path.with_suffix(".vyi"))
             assert isinstance(file, FileInput)  # mypy hint
             module_ast = self._ast_from_file(file)
+            self.resolve_imports(module_ast)
 
             # language does not yet allow recursion for vyi files
             # self.resolve_imports(module_ast)