The cached memory start was not preserved across stack checks in debug
code. This only manifests if the stack check is actually executed, hence
it's tricky to reproduce.

R=ahaas@chromium.org

Bug: chromium:1222648
Change-Id: I8d678305022e3521bd457ad49ebed30d81b05231
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2987824
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75388}