chore: add types to most of the uproot.source module

[lobis]

Add types to most of the sources module.

Only added types where I was sure of the type.

I left things such as urls, file paths, etc. untyped instead of typing them as str since user may pass a pathlib path or similar.

[jpivarski]

Great, thanks! You can merge this as-is. My suggested commits below are just taking the typing further, which is optional.

All of the int argument types are a little dubious: these arguments sometimes take np.int64 and similar, depending on where the integer came from, and that's technically not an int. For runtime type-checking, I use

isinstance(x, numbers.Integral)

which takes NumPy integers as well as Python int, but I think that filling up these files with : numbers.Integral and especially : list[(numbers.Integral, numbers.Integral)] would obscure it.

[jpivarski]

See handle_multipart for comments on futures and results.

[agoose77]

For posterity, I don't think mypy understands the integral type. Also, there's the os.PathLike interface for non-str/bytes types, so we could define that in a local types module.