Add types

[last-partizan]

This PR adds types.

Partially, from https://github.com/sbdchd/mongo-types/ by @sbdchd
Partially, generated by monkeytype
Partially handwritten and generated by included gen.py script (i'll remove it before merging)

I inlined most of the types, but fieds require lot of @overloads - so i put that into separate .pyi.

Note to self, check:

• Passing generic types to fields when using string (like ReferenceField[Image]('Image'))

[last-partizan]

@bagerard And now i need some guidance.

How to best approach testing types? For start i just put some tests into 'tests/test_typing.yml`, but running these tests requires mypy and all optional dependencies.

And that's probably will be slowest tests, due to mypy being not so fast.

pytest tests/test_typing.yml  18.11s user 0.98s system 99% cpu 19.144 total

If speed is a priority, we can put this into separate folder and run once on single python version.
But, we can also run this on all supported python versions (greater than 3.9) - this is probably better, but slower option.