Add pattern index tooltip to tilemap and tileset editor

Just a little UI convenience feature. Knowing the index (without having
to count manually) is convenient when working with tile patterns
programmatically, especially when having lots of them.

editor/plugins/tiles/tile_map_editor.cpp

@@ -321,6 +321,7 @@ void TileMapEditorTilesPlugin::_update_patterns_list() {
 	for (int i = 0; i < tile_set->get_patterns_count(); i++) {
 		int id = patterns_item_list->add_item("");
 		patterns_item_list->set_item_metadata(id, tile_set->get_pattern(i));
+		patterns_item_list->set_item_tooltip(id, vformat(TTR("Index: %d"), i));
 		TilesEditorPlugin::get_singleton()->queue_pattern_preview(tile_set, tile_set->get_pattern(i), callable_mp(this, &TileMapEditorTilesPlugin::_pattern_preview_done));
 	}
 

editor/plugins/tiles/tile_set_editor.cpp

@@ -418,6 +418,7 @@ void TileSetEditor::_update_patterns_list() {
 	for (int i = 0; i < tile_set->get_patterns_count(); i++) {
 		int id = patterns_item_list->add_item("");
 		patterns_item_list->set_item_metadata(id, tile_set->get_pattern(i));
+		patterns_item_list->set_item_tooltip(id, vformat(TTR("Index: %d"), i));
 		TilesEditorPlugin::get_singleton()->queue_pattern_preview(tile_set, tile_set->get_pattern(i), callable_mp(this, &TileSetEditor::_pattern_preview_done));
 	}