This extends the ExpectedOutProc runner to print a diff between the
expected and actual output. The behavior of other runners is unchanged.

Change-Id: If2b89d39cf98b8d257b1a209b5471a79ec3868ff
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3771641Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Liviu Rau <liviurau@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Auto-Submit: Matthias Liedtke <mliedtke@google.com>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81966}