phpstan extensions

[dgoosens]

hi @jakzal

After quite some time, I'd like to follow up on #352

Was able to play with it a little more and think I figured out what went wrong, and how to solve the issue.

The problem is, the toolbox comes with a series of preinstalled phpstan-extension.
As long as the phpstan/extension-installer is not installed, these remain disabled... but as soon as you install the phpstan/extension-installer, all the extensions are enabled and, this does cause a tremendous number of issues.

First of all, IMHO there are some extensions that are rather "niche", ie highly doubt most users will require them. For instance pepakriz/phpstan-exception-rules which will complain for all the missing @throw attributes. An other one is phpstan/phpstan-strict-rules which is VERY opinionated on quite some practices... Finally, ergebnis/phpstan-rules, very opinionated as well and some "questionable" choices IMHO.

As I said, currently, these extensions are installed, but inactive as the phpstan/extension-installer is not preinstalled... So as yet, they are really useless...
And when someone wants some extensions, for instance, in my case phpstan/phpstan-doctrine and phpstan/phpstan-symfony, causes quite some annoyance as I needed to remove the preinstalled extensions.

IMHO it might be better:

1. to remove all the extensions BUT have phpstan/extension-installer installed and enabled by default
2. optionally, add a Docker option to install and enable the extensions the users really want (this option should also be available via docker-compose)

I'm not sure I will have the time in the coming weeks to submit a PR in this regards...
But figured it did make sense to start a discussion about it and, if any other dev has more time to look into it....

Have a nice day
Dmitri