Conditional compilation with @if/@ifnot is now allowed for
- statements
- typeswitch cases
- enum constants
- bitfield struct fields
- struct fields and methods

Bug: v8:7793
Change-Id: I701e8b1f4fb5c5494eaf0af6d0b540bc9166b5ca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3296283Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78060}