Add the build flag `v8_enable_pointer_compression_8gb` which will enable
aligning all alocations to at least 8 bytes, instead of 4. The build
flag will affect tagged values (Smis and compressed pointers) that are
now aligned to 4 bytes. This new alignment is needed to support larger
V8 cages, with sizes of 8GB and larger.

Bug: v8:13070
Change-Id: I15fe1e0c8e0a105e831b756f502a4fcbf72f45a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3757891Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Teo Dutu <teodutu@google.com>
Cr-Commit-Position: refs/heads/main@{#81748}