Attempt to fix regressions introduced by:
https://chromium-review.googlesource.com/c/v8/v8/+/2235117
{current_hint_position_} is not precise enough and can be null even if
the range contains hints.
Instead, repurpose it during register allocation so that it always holds
the last hint position found for this top level live range. This ensures
that each use position is visited at most once even when the range is
split.

R=neis@chromium.org
CC=​sigurds@chromium.org

Bug: v8:10533, chromium:1093435
Change-Id: I21f3f12f061c3e4c7e845d161b19de7499200c0c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2239568
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68319}