chore: phpstan modify

In this commit, modifications have been made to the .gitlab-ci.yml file to allow running PHPUnit on
PHP 8.3 in our pipeline. A new job `modify-job` was added which runs phpstan script with following
instructions:

- Keeping other autoloaders with `QUIQQER_OTHER_AUTOLOADERS=KEEP`
- Disabling progress display with `--no-progress`
- Removing memory limit with `--memory-limit=-1`
- Enabling debug mode with `--debug`