So far the slot is set to 0; in an upcoming CL it will be
used for an actual feedback vector.

Bug: v8:7748
Change-Id: I79f7502757d2cd8b07ced7105bf7532f5bc9b4f0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3205898
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77279}