The graph assembler calls MergeControlToEnd as part of Unreachable
node creation; this causes issues when used inside the GraphReducer
framework, since the reducer is not notified by gasm that the end node
should be revisited.

The (hacky) fix in this CL is to always mark the end node for
revisitation after a gasm reduction has taken place.

Bug: v8:8888,chromium:1123379
Change-Id: I350bb7144add04a0c3fd7f3d88c07fcfe1cd42e3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2384772
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69619}