feat: update PHPStan lvl to 5

[SMillerDev]

This updates the PHPStan check to lvl 5. There are still some unresolved issues and the method types are based on the redis docs so might not be complete.

[pprkut]

For a couple of type changes you can have a look at #92. Or wait until that one is in. It should make a couple things easier.

[SMillerDev]

Updated based on the latest state of the develop branch.

[pprkut]

For the one remaining failure, it looks like the documentation for blpop in Credis is incomplete. It does, in fact, allow an array input.
https://github.com/colinmollenhour/credis/blob/v1.16.2/Client.php#L1670 will take the list of strings we pass in https://github.com/resque/php-resque/blob/develop/lib/Resque.php#L195 and make it a vararg essentially, so the signature is more like blpop(string $key1, string $key2, string $key3, ..., int $timeout), but that's obviously not supported by PHP.

I think adjusting that to string|string[] should be good enough.

[pprkut]

I won't stop you from pushing ahead here, but I feel like scope-creep is setting in 🙂
We don't need to push to level 5 directly, we can totally do intermediate steps which would keep the changes more manageable IMHO. But I leave that up to you

[SMillerDev]

I think it was mostly editing in the web UI that made it seem bad. I've covered everything now, except the fact that $instance can be unset but phpstan doesn't acknowledge that.

[danhunsaker]

$instance can be unset but phpstan doesn't acknowledge that.

With a type hint that doesn't include an uninitialized value as an option, it can't assume null is valid. Add |null and it should sort itself.

[SMillerDev]

Add |null and it should sort itself.

Yeah, I had that until #91 (comment)

[pprkut]

I'll check it some more. Especially in newer PHP versions the assumption of "unitinitialized == null" is no longer true, that's why I don't think adding a type hint for it is correct. But maybe it's the simplest solution.