Trimming is required before the Typer phase to ensure that all nodes
that might be reached via use links have been typed.

Add this phase back on the (background thread) OptimizeGraph
step instead of the (main-thread) CreateGraph phase since there
is no need to do it on the main thread.

BUG=chromium:1212244

Change-Id: I136aadb62d623c8f1898e4e9c0441266d5690be6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2912709Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74733}