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/DOM/Event.idl

@@ -1,7 +1,7 @@
 #import <DOM/EventTarget.idl>
 
 // https://dom.spec.whatwg.org/#event
-[Exposed=*]
+[Exposed=*, UseNewAKString]
 interface Event {
 
     constructor(DOMString type, optional EventInit eventInitDict = {});