LibWeb: Port {Mouse,UI,Wheel,}Event to new String

This ports MouseEvent, UIEvent, WheelEvent, and Event to new String.
They all had a dependency to T::create() in
WebDriverConnection::fire_an_event() and therefore had to be ported in
the same commit.

Userland/Libraries/LibWeb/UIEvents/UIEvent.idl

@@ -1,7 +1,7 @@
 #import <DOM/Event.idl>
 
 // https://w3c.github.io/uievents/#uievent
-[Exposed=Window]
+[Exposed=Window, UseNewAKString]
 interface UIEvent : Event {
     constructor(DOMString type, optional UIEventInit eventInitDict = {});
     readonly attribute Window? view;