[Config] Move from magic loading of all PHPStan extensions, their bootstrap files etc. under control with explicit file listing

[TomasVotruba]

At the start, we required explicit custom configuration for PHPStan being registered in phpstan-for-rector.neon.

In some point we added magic loading of all phpstan extensions, like PHPStan does. The problem is, the more complex the extension became, the more feature we had to mimic from PHPStan container - rectorphp/rector#7795

Instead of continuing in this trend, we better move back to explicit registration of condig in phpstan.neon and let PHPStan container factory handle the job 👍

# phpstan-for-rector.neon
includes:
    - vendor/symplify/phpstan-rules/config/symplify-rules.neon

That way it's clear what is being used in Rector and what not.

Rector extension rules should not depend on PHPStan extension much, as they should handle upgrades of known type declaratoins. For inspiration on those rules, check https://github.com/rectorphp/rector-symfony

[samsonasik]

/cc @mfrieling @mglaman @staabm @sboden @AlexSkrypnyk @tr33m4n FYI

[clxmstaab]

since this PR, we have to configure rector in the "old manual way" while in tandem use PHPStan with the more comfortable autoloading way.

configuring extensions manually is a mess..

the PR describes the main motivation is keeping up with PHPStan on this topic and fixing things when PHPStan moves forward.. maybe we can instead change PHPStan in a way, that rector can re-use the implementation instead of duplicate the logic.

@ondrejmirtes do you agree we could add the extension installer related parts to PHPStan @api surface?

[ondrejmirtes]

@clxmstaab Please open a GitHub issue on PHPStan's side and describe in detail what you want to achieve.