refactor(bar): use Gtk enums for position and orientation

Ensure that the position and the corresponding CSS class on window are
always set.

src/modules/keyboard_state.cpp

@@ -81,7 +81,7 @@ auto supportsLockStates(const libevdev* dev) -> bool {
 waybar::modules::KeyboardState::KeyboardState(const std::string& id, const Bar& bar,
                                               const Json::Value& config)
     : AModule(config, "keyboard-state", id, false, !config["disable-scroll"].asBool()),
-      box_(bar.vertical ? Gtk::ORIENTATION_VERTICAL : Gtk::ORIENTATION_HORIZONTAL, 0),
+      box_(bar.orientation, 0),
       numlock_label_(""),
       capslock_label_(""),
       numlock_format_(config_["format"].isString() ? config_["format"].asString()