After introducing explicit compress and decompress nodes for each load
and store we are left with many nodes that are redundant.

This CL aims to eliminate redundant decompressions and compressions in the
"direct decompression & compression" category.

Also added tests to test the new reducer.

Cq-Include-Trybots: luci.v8.try:v8_linux64_pointer_compression_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_linux64_arm64_pointer_compression_rel_ng
Bug: v8:8977, v8:7703
Change-Id: I93e024d13af34d484086b7983f379265d16ac154
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1602702Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61473}