This CL introduces
 - Member
 - WeakMember
 - UntracedMember
interfaces. Remaining work is to add pointer verifier and write barrier
implementation.

Bug: chromium:1056170
Change-Id: Iddb8e4d002db0b1d1652f2946ddfa08a98a889c7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2124323
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66927}