This CL aims to address the regressions that we saw in Octane 2.1,
particularly in the DeltaBlue test.

This CL brings a 5% improvement in said test by doing
CompressedSigned -> Word32 conversion (instead of
CompressedSigned -> TaggedSigned -> Word32).

There seems to be room for optimizations doing more specialized conversions
regarding representation changes.

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: v8:7703
Change-Id: I24e5b6c06436fdda9fa6a1ac4699dc55c3d67abd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1684075
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62557}