[ticket/17543] Adjust PHPUnit XML configuration
Define source code directories to test and restrict reporting
of deprecation errors to them only to avoid getting this kind
of errors from the 3rd party software and temporary/cache files.
[ticket/17543] Remove ReflectionProperty::setAccessible() method calls
As of PHP 8.1.0, calling this method has no effect; all properties
are accessible by default. The method is deprecated since PHP 8.5.
