Refactor write barriers and split calls, as e.g. DijkstraWriteBarrier
also contained logic for recording slots (cards) for the young
generation.

The new API exposes the following:
- GetWriteBarrierType(): Retrieving the type of barrier that must be
  emitted;
- DijkstraWriteBarrier(), DijkstraWriteBarrierRange(): Dijkstra-style
  write barriers;
- SteeleWriteBarrier(): Steele-style write barrier;
- GenerationalBarrier(): Barrier for recording slots when using
  multiple generations;

Compilers running with -O3 optimize the DijkstraWriteBarrierPolicy
down to the same instructions as before the split.

Change-Id: If68839cc6357b2f568986c9ce8ca753b1e96a70a
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2557514
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71407}