This CL try to use a phi as a branch condition if the control flow from the
branch is known from previous conditions. This change will open up more branch
folding opportunities for later pass.

Change-Id: I26316ab3a68c2d58d0df53691981288a996d4ba1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1674484
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63434}