This reverts commit 6ec7be21.

Reason for revert: Speculative revert for https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Win64/47984/overview

Original change's description:
> [sandbox] Sandboxify WasmExportedFunctionData::sig
>
> This CL changes the WasmExportedFunctionData class to store a direct
> ExternalPointer to the wasm::FunctionSig instead of referencing it
> through a Foreign. This in turn makes it possible to use a unique
> pointer tag for that external pointer when the sandbox is enabled.
>
> Drive-by: move WasmInternalFunction::call_target external pointer to the
> end of the object, in line with other external pointer fields.
>
> Bug: v8:10391, v8:12949
> Change-Id: Ic3ff622a075c9eaa2f8d8835803437466290c928
> 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/+/3829086
> Commit-Queue: Samuel Groß <saelo@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#82523}

Bug: v8:10391, v8:12949
Change-Id: I18a7c9603e30d7cd78fd599e59596015260a5818
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/+/3834259
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82535}