Termination GCs are used to destroy remaining C++ object on the
managed heap to free potential off-heap memory. This is important for
gracefully shutting down workers.

Drive-by: Add guard prohibiting recursive sweeping calls on the
  mutator thread.

Bug: chromium:1056170
Change-Id: I02ea3b632d38f5beab18cc8f077cf717ed877909
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2631504
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72155}