CompressedHeapConstant is used in the DecompressionElimination Reducer to
create compressed HeapConstant values. It won't appear in the graph
up until that point.

This CL enables back the disabled tests in DecompressionElimination, as
well as generating the CompressedHeapConstant in that reducer.

The RelocInfo has already been added for x64 but not for arm64. Therefore,
the x64 version is now doing the mov on 32 bits. The support for ARM will
come in a following CL, and for now it is doing the mov in 64 bits.

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, v8:9298
Change-Id: If0ca4f937cfa60501679e66f6fd5ded2df38f605
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1632236Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61950}