The main change is about tracking typed slots locally in
each concurrent marking thread.

This generalizes the old LiveBytesMap to MemoryChunkData, which
now contains the live bytes and the typed slots.

With that in place it is straightforward to mark code concurrently.

Bug: v8:8459
Change-Id: I103fff0ad39beadea5151a1d8519f5d3c6602e58
Reviewed-on: https://chromium-review.googlesource.com/c/1337747
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58072}