bindings: Support Web IDL async iterable (3 of 4)

Supports the code generation of AsyncIterator<Foo> and
V8AsyncIteratorFoo for interface Foo that declares async iterable.

AsyncIterator<Foo> and V8AsyncIteratorFoo are mostly the same as
SyncIterator<Foo> and V8SyncIterableBar. The key differences are:
1. prototype chain (v8::Intrinsic::kAsyncIteratorPrototype)
2. @@asyncIterator property (instead of @@iterator property)

Bug: 1087157
Change-Id: I8c48ef730b953eadca1046ac69f5aeeb6752310a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4666961
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Raphael Kubo Da Costa <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/main@{#1184089}