Store the is_marking_flag_ in the IsolateData to improve the generated
code for the RecordWrite builtin. This allows to load the value of the
flag directly using the root register, instead of loading that flag's
address first using the root register and only then loading its value.

Bug: v8:11708
Change-Id: Id4076a7e519c5f8126e310771c0ccd958dc07278
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3780536
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82456}