Natively implement "PS256/PS384/PS512"

Apparantly PHP 8.5.0 added a new optional parameter to openssl_sign() and openssl_verify(), according to the changelog and status of https://bugs.php.net/bug.php?id=80495

I haven't investigated anything about usage at all, as the php manual is quite slim about details as usual.

As an additional task, we'd need to figure out a way to integrate it into the core lib, as the required parameter isn't available for PHP 8.4 - probably hold back on releasing anything until 8.5 is the lowest supported version, I suppose.