Need to use relaxed store for initializing bit_field. The concurrent marker accesses the has_prototype_slot bit in Map::bit_field to calculate header size.

Bug: v8:10315
Change-Id: I1eebd4a6f42b9263de7e424957b32884f7b910ad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2193712
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67710}