Use InputMap actions consistently across all LineEdit's that filter an underlying Tree or ItemList.

- Instead of checking for Key::UP, Key::DOWN, Key::PAGEUP, Key::PAGEDOWN etc., we rather check for the action like 'ui_up' or 'ui_down'.
- Also use AcceptDialog's 'register_text_enter' functionality to consistently close a dialog when ENTER is pressed while the LineEdit has focus (instead of redirecting ENTER keys to e.g. the underlying Tree).
- Unify the LineEdit filter behavior for the SceneTreeDialog and corresponding usages
- Improve OK Button disablement (something should be selected)

editor/editor_command_palette.cpp

@@ -183,18 +183,13 @@ void EditorCommandPalette::_notification(int p_what) {
 	}
 }
 
-void EditorCommandPalette::_sbox_input(const Ref<InputEvent> &p_ie) {
-	Ref<InputEventKey> k = p_ie;
-	if (k.is_valid()) {
-		switch (k->get_keycode()) {
-			case Key::UP:
-			case Key::DOWN:
-			case Key::PAGEUP:
-			case Key::PAGEDOWN: {
-				search_options->gui_input(k);
-			} break;
-			default:
-				break;
+void EditorCommandPalette::_sbox_input(const Ref<InputEvent> &p_event) {
+	// Redirect navigational key events to the tree.
+	Ref<InputEventKey> key = p_event;
+	if (key.is_valid()) {
+		if (key->is_action("ui_up", true) || key->is_action("ui_down", true) || key->is_action("ui_page_up") || key->is_action("ui_page_down")) {
+			search_options->gui_input(key);
+			command_search_box->accept_event();
 		}
 	}
 }