- Remove flag --block-concurrent-recompilation and its implementation,
  including %UnblockConcurrentCompilation.
- Rewrite tests that used it in terms of the primitives introduced in
  my previous CL:
  https://chromium-review.googlesource.com/c/v8/v8/+/3071400/
- Remove "sync"/"no sync" arguments from %GetOptimizationStatus,
  assertOptimized, etc. These are now always "no sync": they don't
  do any magic.
- Remove "if %IsConcurrentRecompilationSupported then quit" from some
  tests in favor of --concurrent-recompilation in their Flags line.

Bug: v8:12041, v8:7790
Change-Id: I966aae4fec85e6f9e7aeed2ba2c12e9198a3991f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3077149Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76298}