Set editor's translation domain at root node

[timothyqiu]

@KoBeWi found that some strings in the save file confirm dialog are not translated (e.g. window title):

This is because the dialog has recently been given the possibility to be reparented to the root node. However, the translation domain of the editor only takes effect on the EditorNode node, so auto translation won't work.

godot/editor/editor_node.cpp

Lines 5750 to 5754 in 15ff450

	void EditorNode::_prepare_save_confirmation_popup() {
	if (save_confirmation->get_window() != get_last_exclusive_window()) {
	save_confirmation->reparent(get_last_exclusive_window());
	}
	}

Changing the translation domain to be set at the root node can also help to resolve other potential similar issues as well.