Rename flags to align them with other flags that are named in an
enabled way and drop the "never" prefix.

Drive-by: Refactor compaction entry point.

Bug: v8:12251
Change-Id: If2b189152f3cd22038b87fe3cc2ba0db4953ae23
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3270534
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77813}