Add clear text button to LineEdit

- Add pressed state to clear button
- Enable clear button on all inputs with search icon
- Remove duplicate clear buttons
- Fix rendering of icon for center and right alignments
- Add clear button to more search fields
- Add clear icon to default theme
- Add method to control enabled state of clear button
- Add property to enable clear button from inspector

editor/quick_open.cpp

@@ -258,6 +258,9 @@ void EditorQuickOpen::_notification(int p_what) {
 	if (p_what == NOTIFICATION_ENTER_TREE) {
 
 		connect("confirmed", this, "_confirmed");
+
+		search_box->add_icon_override("right_icon", get_icon("Search", "EditorIcons"));
+		search_box->set_clear_button_enabled(true);
 	}
 }