We have to have special rules for bit_fields since we multiple accesors
touch the same field. I used:
 * If the accessor is set at map initalization time only and:
   * only the main thread accesses it: non-atomic write/read
   * bg accesses it too: non-atomic write, relaxed read (read has to be
     relaxed due to the whole bit_field being modified concurrently via
     other bit_field3 accessors)
 * If the accessor is set after map initialization:
   * but it is not necessary for synchronization: relaxed write/read
   * If the accessor is needed for synchronization: release/acquire

As a note, Map::NumberOfOwnDescriptors are the bits accessed by the
concurrent marker. For concurrent marker reasons it can be relaxed, but
we would like it to be release/acquire for the compiler since that's
where we synchronize Maps with adding descriptors to the descriptor
array.

Bug: v8:7790, chromium:1150811
Change-Id: I0ba7d2f8cb81d65a487970b4ea0bfa2a4cb3a975
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2773286Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73911}