This reverts commit a4c37558.

Reason for revert: Speculative revert.
Seems to break all gpu builders, e.g.:
https://ci.chromium.org/p/v8/builders/ci/Linux%20V8%20FYI%20Release%20(NVIDIA)/14577

See shards for detailed output, e.g.:
https://chromium-swarm.appspot.com/task?id=534a8fbeaca4df10

Check failed: valid_arguments. V8.WasmMemoryProtectionKeysSupport

Original change's description:
> [wasm] Add PKU alloc/free and support counter
>
> To enforce W^X for the WebAssembly code space, we want to explore using
> Intel memory protection keys for userspace, also known as MPK, PKEYs, or
> PKU. Instead of flipping page protection flags with mprotect (which
> incurs a high syscall overhead; and which switches flags for the whole
> process), this associates a key with each page once, and then changes
> the permissions of that key with a fast thread-local register write.
> That is, this gives both finger-grained permissions (per-thread) and
> more performance.
>
> This CL is starts experimenting with PKUs by
> (1) trying to allocate a protection key once per {WasmEngine} in x64
> Linux systems, and
> (2) adding a counter for recording the sucess/failure of that, to assess
> the support for PKUs on the target machine.
>
> The low-level PKU allocating functions should be moved into base/platform
> long-term, but are inside wasm/ for this CL.
>
> R=​clemensb@chromium.org
> CC=​​jkummerow@chromium.org
>
> Bug: v8:11714
> Change-Id: Ia4858970ced4d0b84cc8c2651e86dceb532c88a7
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2850932
> Commit-Queue: Daniel Lehmann <dlehmann@google.com>
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74319}

Bug: v8:11714
Change-Id: I70349d413ac9092e2f033d138887678bfecaae17
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2868607
Auto-Submit: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#74339}