The operator with raw pointer allows us to avoid Member decompression,
which is more expensive than compression. It's also quite frequently
called (e.g. in HeapHashSet::find()).

The existing operator
  template <...>
  bool operator==(const Member<T1>&, const Member<T2>&);
was not called for
  GCed* raw = ...;
  member == raw;
because the compiler wouldn't deduce `T2` in `const Member<T2>` as
`GCed` when the initializer expression `raw` is of different type
(`GCed*`).

Bug: chromium:1325007
Change-Id: Ie1ee12bad28081c66f4e08a146467fd7c040bb70
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3757344Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81702}