When we can eliminate a branch-on-type instruction based on statically
available type information and replace it with an unconditional branch,
we have to mark the rest of the current block as unreachable.

Change-Id: I9b8cc2f8e76da0b1b7cdf72b150ec675e9aae1a3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3490931Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79288}