That DCHECK could fail even though GC was in the right state. It could
happen that the first load gets the old value NOT_IN_GC, since this
isn't TEAR_DOWN a second load needs to be performed. The load then
returns TEAR_DOWN but that doesn't match NOT_IN_GC either.

Fix this by only loading gc_state() once.

Bug: v8:10315
Change-Id: Ibcad540fa4d5f578c9936c472b294bbccebdc09a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2418719Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70021}