This adds some basic tests for WebAssembly code protection, in four
different configurations:
- no protection
- mprotect-based protection
- PKU-based protection
- PKU with fallback to mprotect

If PKU is not supported by the OS or hardware, then PKU is identical to
no protection, and PKU with fallback is identical to mprotect. We always
execute all four configurations anyway.
If protection is effective, we expect code to be writable within a
{CodeSpaceWriteScope}, and not writable otherwise. When trying to write
to non-writable code, we expect a crash of the process (checked via
{ASSERT_DEATH_IF_SUPPORTED}).

R=jkummerow@chromium.org
CC=​mpdenton@chromium.org

Bug: v8:11974
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_dbg_ng
Change-Id: I4ec0ce9426f70ff41a292b9ea25be1e8956a670e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3138210
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76726}