This is a reland of commit efac35f3

The LSan issues have been fixed in https://crrev.com/c/3779915

Original change's description:
> [sandbox] Sandboxify JSExternalObject external pointer
>
> Bug: v8:10391
> Change-Id: I6075a8fe3c201f9221149e0c54edf4fb191088da
> 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/+/3757342
> Commit-Queue: Samuel Groß <saelo@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#81924}

Bug: v8:10391
Change-Id: I954520ee324c9aa4c4ccc4941ae30d19676be2ba
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/+/3780501Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81978}