The regexp stack is used during execution of jitted regexp matcher
code.  Previously, the stack was initially not present / nullptr, and
we had to explicitly check for this condition and bail out in builtin
code.

This CL changes behavior to guarantee a present stack by adding a
statically-allocated area that is used whenever no
dynamically-allocated stack exists.

Change-Id: I52934425ae72cf0e5d13fab2b9d63d37ca76fcf3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1852126
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64326}