Avoids emitting scopes when not even running. This can be a problem for
metrics computation which may recursively invoke
EnsureSweepingCompleted() when starting marking even though the sweeper
is guaranteed to be not running at this point.

Bug: chromium:1211795
Change-Id: I8d7692f4e8c640f38d3c52df5c111fff4f06df9e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3109674
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76411}