In order to support a larger heap cage (8GB, 16GB), the cage offset
will take up more than 32 bits. As a consequence, for 8GB cages, the
least significant bit of the cage offset will overlap with the most
significant bit of the tagged offset. To avoid this, allocations need
to be aligned to 8 bytes to free up one bit from the offset.
All changes are deactivated behind the build flag
`v8_enable_pointer_compression_8gb`.

Bug: v8:13070
Change-Id: Ibb0bd0177f3e88dcd24fc0ee7526335df0faa987
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3791052Reviewed-by: Igor Sheludko <ishell@chromium.org>
Auto-Submit: Teo Dutu <teodutu@google.com>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82299}