fix: Gutter icons in the editor for trait scripts

Credit @Ward727a

- Fixed a bug when 2 functions (one from trait, and one from other scipt) was one the same line: The gutter icon for virtual function wasn't shown.

- Did a little optimization on the "get_function_names_recursively" function (using Vector and not HashMap) this allow us to gain ~10% in time when running (HashMap average ~= 9.8µs / Vector average ~= 8.8µs).

Author: decryptedchaos

modules/gdscript/gdscript_editor.cpp

@@ -198,7 +198,6 @@ bool GDScriptLanguage::validate(const String &p_script, const String &p_path, Li
 		get_function_names_recursively(cl, "", funcs);
 
 		for (const String &E : funcs) {
-			r_functions->push_back(E);
 		}
 	}