- Add v8_code_comments to allow runtime-enabled code comments with
  --code-comments
- v8_code_comments is enable by default in debug mode
- Make MacroAssembler::RecordComment helper inlineable to remove
  call and check overheads when v8_code_comments = false
- Make FLAG_code_comments readonly if v8_code_comments = false and
  benefit from dead-code elimination

This saves roughly 5% CompileBaselineVisit time in sparkplug
on a 5MiB JS file.

Bug: v8:11420
Change-Id: I1174ab37b4bbe1ff8880416c1f6a6e28377a962c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2824428Reviewed-by: Bill Budge <bbudge@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74055}