Use C23 memset_explicit() for ZEND_SECURE_ZERO() if available

[Girgias]

Description

This new function is designed to never be optimized away by a compiler.

I think this needs some configure checks, which I never know how to do. @petk do you know if anything fancy needs to be done?
We probably also want to amend the implementation of php_explicit_bzero() to use this if available.

[petk]

From what I see, it only needs to be checked in the AC_CHECK_FUNCS([memset_explicit]) somewhere - in configure.ac probably and then used conditionally:

#ifdef HAVE_MEMSET_EXPLICIT
...
#else
...
#endif

Except that on Windows, it's probably not available (yet).

[cmb69]

Except that on Windows, it's probably not available (yet).

I think so, too, at least regarding MSVC; not sure about clang on Windows, though.