Unify macOS ARM64 write protection holders with W^X ones (#54067)

Unify macOS ARM64 write protection holders with W^X ones (#54067)

* Unify macOS ARM64 write protection holders with W^X ones

This change removes the original holders that were added for changing
memory protection for executable code and moves the actual switching to
the recently added W^X holders.

The unixexports files don't support target specific symbols. So I needed
to export a dummy version of the PAL_JitWriteProtect for macOS x64.