To be able to use PHPStan's caching mechanism for generating
factory & proxy classes, a simplified version of a file cache
storage is added.

Unfortunately made it impossible to overload the autoloader and
magically set the custom autoloaders needed for the extension to
run. Thus I removed the registration.php file handled the magic.

This means regardless of using the .phar archive or phpstan-src
dependency, you have to manually configure the autoload.php
work-a-round in the project's phpstan configuration.

To make sure that the cached files are generated in the
same cache directory as the regular phpstan files, find
the phpstan configuration and parse it via Nette\Neon
parser. Downside: The configuration gets parsed twice but
I did not notice any bigger speed difference.