Move Ui header items to OpenRCT2::Ui (#21546)

* Move ui definitions to ui project

* Enforce coding style

* Apply clang format

* Add clang tidy ignore

* Increase compiler happiness

src/openrct2-ui/windows/Dropdown.cpp

@@ -45,7 +45,7 @@ enum
 
 static Widget window_dropdown_widgets[] = {
     MakeWidget({ 0, 0 }, { 1, 1 }, WindowWidgetType::ImgBtn, WindowColour::Primary),
-    WIDGETS_END,
+    kWidgetsEnd,
 };
 
 int32_t gDropdownNumItems;