[TASK] Add fallback mechanism to load default extensions

[sabbelasichon]

• If the rector-installer failed or is not executed due to --no-scripts flag at least the old default extensions are loaded

Resolves: #6347

[TomasVotruba]

I'm not sure having 2 ways to install packages is a good approach. This is what we had before and tried to get rid of :)
Devs need to learn the package is installing extension, like we did with PHPStan installer and flex installer.

IMO that reported bug is a wrong abstraction in our part. Mismatch of tags with non-existing class or something.

[sabbelasichon]

@TomasVotruba It is meant as a fallback solution to circumvent this error. It is always the rector-nette package. Maybe it is sufficient to only add this package here. I have never looked closely to the bug. But maybe we can get rid of after some time.

[TomasVotruba]

That's the composer install convention on any plugin. I've decoupled NetteToSymfony to own package to remove core dependency on extension: #6360