On success the call never returns — the process image is replaced.
Another program that loads PHPStan's phar, Rector for example, passes
the path to that phar: Phar::running() only knows the phar that runs.
Without $appName only what the turbo extension needs is restarted for,
as before. With it, the same single restart also neutralizes xdebug,
pcov and the other hooks PHPStan's own restart does, unless --xdebug is
in $argv or <APP>_ALLOW_XDEBUG is set - the variable composer/xdebug-handler
reads for that application, so a caller can drop its own xdebug restart.