Add PHPStan\Rules\Classes\AccessPrivateConstantThroughStaticRule to PHPStan rules

I think this would prevent hitting the linked issue, but I think this is addressing the symptom not the cause.

I still think the root cause is using private in the first place.

@nicxvan I disagree. The root cause is using stattic:: to get a private const - which this detects. Private constants in an of themselves are not the root cause. We have the same issue with a private static method... that should never be called using static:: either - it would cause the same problems.

And for that matter any private static variable - they should be never be accessed with static:: unless the class is final...