script_bindings: Assert that serializable/transferable types have accurate WebIDL annotations (#38615)

These changes add compile-time assertions that:
* any type that implements the Serializable/Transferable trait has a
`[Serializable]` or `[Transferable]` annotation in the interface WebIDL
* any WebIDL interface with the `[Serializable]` or `[Transferable]`
annotation implements the corresponding trait

This is useful because it means that WebIDL definitions will be less
confusing if you're trying to figure out whether Servo supports
serializing/transferring a particular interface type. It also makes
fixing #21715 in the future a little bit easier, because the annotations
will remain up to date.

Testing: compile-time only; no point in writing tests for this since it
involves webidl codegen.

---------

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

components/script_bindings/webidls/WritableStream.webidl

@@ -4,7 +4,7 @@
 
 // https://streams.spec.whatwg.org/#writablestream
 
-[Exposed=*] // [Transferable] - See Bug 1562065
+[Exposed=*, Transferable]
 interface WritableStream {
   [Throws]
   constructor(optional object underlyingSink, optional QueuingStrategy strategy = {});