Bug 1773070 - Unify Gecko and Servo EventState/ElementState bits. r=smaug

Add a dom/base/rust crate called just "dom" where we can share these.

Most of the changes are automatic:

  s/mozilla::EventStates/mozilla::dom::ElementState/
  s/EventStates/ElementState/
  s/NS_EVENT_STATE_/ElementState::/
  s/NS_DOCUMENT_STATE_/DocumentState::/

And so on. This requires a new cbindgen version to avoid ugly casts for
large shifts.

Differential Revision: https://phabricator.services.mozilla.com/D148537

dom/html/HTMLFormElement.h

@@ -76,7 +76,7 @@ class HTMLFormElement final : public nsGenericHTMLElement,
   virtual void SetValueMissingState(const nsAString& aName,
                                     bool aValue) override;
 
-  virtual EventStates IntrinsicState() const override;
+  virtual ElementState IntrinsicState() const override;
 
   // EventTarget
   virtual void AsyncEventRunning(AsyncEventDispatcher* aEvent) override;