Split off MarkingWorklists and from Marker and introduce MarkerBase.

MarkerBase refers just to interfaces types for passing along visitors.
The concrete Marker provides the impl for these interfaces. Unified
heap marker uses different marking visitors internally but provides an
implementation for the same interface.

Change-Id: Ibc4b2c88e2e69bd303a95da7d167a701934f4a07
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2270539
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68676}