[FEAT] Should teach `py::type::of<>` to handle non-generic types

[EricCousineau-TRI]

See discussions in #2364:

• feat: py::type::of<T>() and py::type::of(h) #2364 (comment)
• feat: py::type::of<T>() and py::type::of(h) #2364 (comment)
• feat: py::type::of<T>() and py::type::of(h) #2364 (comment)

FYI @YannickJadoul @henryiii - Im' filing this pre-emptively ;) Feel free to close this as part of #2364 if y'all incorporate it in that PR.

[YannickJadoul]

No, I agree this can be discussed and put into a new PR! 👍

Also, oops, another comment: #2364 (comment)