Now that everything is properly wired to the effect chain when we get to
ChangeLowering, we can safely inline the allocation fast path and only
need to consule the slow path stub fallback when bump pointer allocation
fails.

R=jarin@chromium.org
BUG=v8:4931
LOG=n

Review-Url: https://codereview.chromium.org/1951853002
Cr-Commit-Position: refs/heads/master@{#36022}