Change config's type to TypedDict instead of Dict.

[JacekDuszenko]

Added a new TypedDict representing config.yaml contents and replaced config's types around the codebase.

@allcontributors please add @JacekDuszenko for code

[yorickvP]

CI failure:

python/cog/predictor.py:28:1: I001 [*] Import block is un-sorted or un-formatted
python/cog/server/http.py:27:1: I001 [*] Import block is un-sorted or un-formatted
python/cog/types.py:1:1: I001 [*] Import block is un-sorted or un-formatted