[code-quality] Add VariableConstFetchToClassConstFetchRector

[TomasVotruba]

Prefer known class, over pseudo-dynamic value:

final class AllowOverride
{
    public function run(KnownClass $classWithConstants)
    {
-        return $classWithConstants::SOME_CONSTANT;
+        return KnownClass::SOME_CONSTANT;
    }
}

[samsonasik]

per rule name, I think this needs to be exactly check against Variable node, check on Expr may cause invalid due to side effect call, eg:

some_side_effect()::NAME;

see https://3v4l.org/UkiYR

I will create new PR to fix it.

[samsonasik]

I created PR

• [CodeQuality] Skip non-variable fetch on VariableConstFetchToClassConstFetchRector as may cause side effect #7464

for it.