Run memory optimizer after all the other graph phases. This is
a step towards enabling allocation folding for arrays with
>16 elements because constant additions will be properly
constant-folded.

Bug: v8:8984
Change-Id: Ia3c78a3bd32264f4f83d3e20bd78abf240d9292b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1539496Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60465}