... mostly by turning them into pointer arguments.

After this CL, all remaining non-const reference arguments in
the compiler directory are in the backend.

Bug: v8:9429
Change-Id: I6a546da0fe93179e1a0b12296632591cbf209808
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1719185Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62930}