Update for PHP 8.1+

[dereuromark]

First stab at #368

It will also require test harness to be fixed up for 8.1+

Declaration of PHP_CodeSniffer\Tests\TestSuite::run(?PHPUnit\Framework\TestResult $result = null) must be compatible with PHPUnit\Framework\TestSuite::run(?PHPUnit\Framework\TestResult $result = null): PHPUnit\Framework\TestResult

As well as (follow-ups?):

• Move tests into tests/ with proper autoload-dev instead of part of autoload

[dereuromark]

I enabled for now the full set of mult-line declarations, just for testing
We can redude this once we are ready for merging if it is too disruptive and only keep 1 of the 3 pairs

For now the pressing question is how to get the tests working on modern versions of dependencies.

[dereuromark]

Anyone any ideas on the blocker of tests getting green again?

[LordSimal]

Whats the state of this PR?

[dereuromark]

This looks like it needs a bit of rework now.
I would still like to see it added

[ADmad]

@dereuromark I see you have added a few more rules regarding trailing comma besides the one I added in #398. So if you want to get them into the next minor now would be the time.

BTW PER 2.0 has added rules regarding trailing comma, so it would be good to follow that https://www.php-fig.org/per/coding-style/#26-trailing-commas

phpcs still doesn't seem to have a PER 2.0 rules set but hopefully it will have one soon making things easier for it.

[dereuromark]

I rebased and ran a test con cakephp/cakephp:
266 more files changed on the function signatures, not sure if we want to do this too
The benefit would be less merge conflicts in the future.

[dereuromark]

I ran into slevomat/coding-standard#1715 by the way, also happens without my updates, so this is an issue we need to tackle separately..

[ADmad]

266 more files changed on the function signatures, not sure if we want to do this too

That's fine, better to stay consistent about the trailing comma along all constructs. It's not a problem as long as it's auto fixable.

I ran into slevomat/coding-standard#1715 by the way

The slevomat guys a usually pretty responsive, so hopefully should be resolved soon.

[dereuromark]

I added PHPStan.
For level 7 there seem to be only a few issues, but we can tackle them also separately afterwards.