PHP 8.5 adoption

Added to test suite in xp-framework/core@009498040 

## Changes in PHP 8.5
See https://wiki.php.net/rfc#php_85

## Initial results
See https://github.com/xp-framework/core/actions/runs/14570004500/job/40865400220:

* [x] realpath(): Argument 1 ($path) must not contain any null bytes)
* [x] Handling of `self` and `parent`
