Instead we only change the map for the node being checked.

This also changes AbstractMaps to look through renames for keys. That
might theoretically lead to seeing less precise types for MayAlias
tests, the hope is it does not matter much.

Bug: v8:6396
Change-Id: I28a067080a3bc58c62a9dd5a76dce1aa348d8e0c
Reviewed-on: https://chromium-review.googlesource.com/730705Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48785}