This reverts commit 49c59678.

Reason for revert: The change is suspected to be breaking chromium's determinism test: https://ci.chromium.org/ui/p/chromium/builders/ci/Deterministic%20Linux/35003/overview

Original change's description:
> [sandbox] Fold V8_SANDBOXED_EXTERNAL_POINTERS into V8_ENABLE_SANDBOX
>
> Now that all external pointers have been sandboxed,
> V8_SANDBOXED_EXTERNAL_POINTERS is no longer needed. This change also
> shrinks external pointer slots to 32 bits when the sandbox is enabled.
>
> Bug: v8:10391
> Change-Id: Iccbef27ac107b988cb23fe9ef66da6fe0bae087a
> Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng,v8_linux_arm64_sim_heap_sandbox_dbg_ng
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3869269
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
> Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Commit-Queue: Samuel Groß <saelo@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#83083}

Bug: v8:10391
Change-Id: I515ba771aa21f58b752a3a5b36b4deb2abc5f9c0
Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng,v8_linux_arm64_sim_heap_sandbox_dbg_ng
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3886870
Commit-Queue: Matthias Liedtke <mliedtke@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Matthias Liedtke <mliedtke@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83111}