Improve Reflection API type hinting

[uuf6429]

• in certain places, it's practically guaranteed that a non-empty-string is expected since symbols cannot have an empty string, so I updated them accordingly
• I've replaced T template type name with something more readable - in one case this even fixed a bug because T was defined for the entire class AND on a specific method.
• when possible, I replace the general array type with something more specific - list or indexed array etc.
• added some missing templates types, mainly on constructors e.g. @template TReflectedClass of UnitEnum

Dislcaimer:

• I was not able to run tests locally, as per Various fixes #1805 (comment)
• It's likely this change might cause static analyser errors in projects using it.

E.g. the following would now fail (but it should have already): https://phpstan.org/r/09d7d483-6aad-41df-805e-75d44edbec32
It's worth noting that now it would also fail in "unsecured" cases e.g. if the method name was retrieved from somewhere returning string instead of non-empty-string