Mutate Type->getConstantScalarTypes() into Type->getFiniteTypes()

[staabm]

to verify small integer ranges are properly supported.

see e.g. https://github.com/phpstan/phpstan-src/pull/4520/files#r2488954576

wdyt?

[ondrejmirtes]

The difference is that with getFiniteTypes, you'll also get something returned from ConstantArrayType and ObjectType (with enums) and IntegerRangeType.

So if a mutant escapes, it's possible that the code is not tested enough, and tests should also cover these cases. Or that it should indeed use getFiniteTypes instead.

BTW can we get some kind of description next to an escaped mutant, like an error message? It'd be useful to describe what to do there.