So far this flag was process-global, so if one isolate used v8::Locker
all isolates were forced to use v8::Locker. With the shared isolate
now being a thing that routinely gets migrated between different
threads, all users of the shared isolate would be forced to use
v8::Locker. So we now store that flag on the isolate such that using
v8::Locker for the shared isolate does not affect other isolates.

Deprecate v8::Locker::WasEverUsed() at the same time.

Bug: v8:11708
Change-Id: I60531f084cc1b1b113620c46f5bed20511f52c26
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3401595Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78712}