There was a missing write barrier for the saved registers and context
in GeneratorStore. Add (deferred) write barriers for these, with some
careful register reshuffling to minimise moves.

Bug: v8:7700
Change-Id: Icf50e96adf3775785ce9b2c5a7566ecbbd1d63d9
Fixed: chromium:1359163
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3870914Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82962}