Add a flag for controlling the maximum number of threads usable by the
LazyCompileDispatcher.

Change-Id: I87fc39d337a00cff0c3d152392630f48da050fff
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3312482
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78214}