LibGUI: Base write_to_file(StringView path) on the stream overload

`write_to_file(StringView path)` was based on the `Core::File` overload.
The return type also changed from `bool` to `ErrorOr<void>` to ease
error propagation.

Userland/DevTools/HackStudio/EditorWrapper.cpp

@@ -79,7 +79,7 @@ void EditorWrapper::save()
         });
         file_picker_action->activate();
     }
-    editor().write_to_file(filename());
+    editor().write_to_file(filename()).release_value_but_fixme_should_propagate_errors();
     update_diff();
     editor().update();
 }