Provides the infrastructure to register weak callbacks for
WeakMember<T> through visitor. The WeakCallbackInfo broker is used to
query objects for liveness. In a future CL the same broker object is
passed to custom weak callbacks.

Change-Id: I8b5a66354e0e457521989d40ae64a9558c339503
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2142265
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67109}