This reverts commit 1f504c36.

Reason for revert: Failures in Chromium tests causing a blocked roll - https://ci.chromium.org/ui/p/chromium/builders/try/linux_chromium_tsan_rel_ng/848645/overview

Original change's description:
> Reland "[ptr-cage] Turn on shared pointer cage by default for arm64 and x64"
>
> This is a reland of 6c65e858
>
> Changes since revert:
>
> - Add --disable-shared-ro-heap-for-testing flag that is implied by
>   d8's --stress-snapshot, since RO heap sharing currently
>   does not support deserializing/serializing while original Isolate
>   is still running
> - Add BUILD.gn assert that v8_enable_pointer_compression_shared_cage
>   requires x64 or arm64
>
> Original change's description:
> > [ptr-cage] Turn on shared pointer cage by default for arm64 and x64
> >
> > Bug: v8:11460
> > Change-Id: I9ab419b5e90fbe677e1d63b41699d90552839e98
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2873226
> > Commit-Queue: Shu-yu Guo <syg@chromium.org>
> > Reviewed-by: Igor Sheludko <ishell@chromium.org>
> > Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> > Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#74422}
>
> Bug: v8:11460
> Change-Id: I7eb189b7f8ac3e30da96b0dadd2c085f08a1a0b1
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2878855
> Commit-Queue: Shu-yu Guo <syg@chromium.org>
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Reviewed-by: Adam Klein <adamk@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Reviewed-by: Dan Elphick <delphick@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74448}

Bug: v8:11460
Change-Id: Ice601be4826adbae1288f3314192bdf6566a366c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2883660
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74473}