Adds basic support for CompressedHeapConstants to Arm64 by moving to a ldr_w
instruction and passing COMPRESSED_EMBEDDED_OBJECT as the RelocInfo. However,
we still haven't made the COMPRESSED_EMBEDDED_OBJECT be actually compressed
in the code-stream (they still take up a full 64-bits). Support for this will
be added next.

Adding a test on macro assembler that checks that the
RelocInfo::COMPRESSED_EMBEDDED_OBJECT is flowing through.

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: Ibc64cdfdd85d5cdfa060ed6227b10bb47eae3a8a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1635692Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62306}