This CL removes the StoreBuffer and inserts slots into the
RememberedSet directly from within the RecordWrite builtin. Only calls
into C code when either the SlotSet-array or the bucket is not
allocated. This avoids filling the store buffer up with duplicates or
due to a write-heavy workload and then blocking the main thread on
store buffer processing.

The first CL (https://crrev.com/c/1815241) got reverted, because
mksnapshot was using a different size for SlotSet than the final
binary on ARM. This is fixed now, SlotSet has a standard layout.

Bug: v8:9454
Change-Id: I881641f4ee08a8b42c36fdca8733138b908096bd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1842452Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64126}