Continuing the cleanups and using the tags rather than synchronized_
in the name of the accessors.

Bug: v8:7790
Change-Id: I3c2d0ccf54fa6161dbd9d12b1b9743a046534521
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2897095Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74609}