.. by reusing the regexp stack from potentially multiple nested
irregexp activations.

To do this, we now maintain a stack pointer in RegExpStack. This stack
pointer is synchronized at all boundaries between generated irregexp
code and the outside world, i.e. when entering or returning from
irregexp code, and when calling into C functions such as GrowStack.

Fixed: v8:11382
Change-Id: I5ed27630c1a64ebf3afb9ddf80fb60ea067c0c40
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3162604Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Patrick Thier <pthier@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77013}