This reverts commit dacce720.

Reason for revert: Needs a fix.

Original change's description:
> [wasm] Fix fallback from PKU to mprotect
>
> The {WasmCodeManager::SetThreadWritable} method would return true if
> called in a nested scope, even if PKU is not available. The caller
> cannot tell then whether permission switching happened or not.
>
> This CL refactors the code to do an explicit check for PKU support, and
> removes the boolean return value from {SetThreadWritable}.
>
> R=​jkummerow@chromium.org
>
> Bug: v8:11959, v8:11974
> Change-Id: I2d45f1fa240305c6f92f63cdf190131d637bfe95
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3021383
> Commit-Queue: Clemens Backes <clemensb@chromium.org>
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#75699}

Bug: v8:11959, v8:11974
Change-Id: I199cf6dd6e12a209649fcf86f922e2500b50bbde
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3021179
Auto-Submit: Clemens Backes <clemensb@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@{#75700}