More patcher typing changes

[Miepee]

seems as good a time as any to leave my general feedback here:

1. I strongly recommend using snake_case keys in the schema for better adherence to the python style guide in the generated TypedDict definitions
2. the KEY_WHATEVER constants are an antipattern imo. using normal string literals will be better for basically everything. if you want to rename a key, rename it in the generated file with your IDE's rename function and then update the schema
3. it's a bit surprising that so many keys in your schema aren't required. I find it's best to have as few optional fields as are necessary. I recommend using the ValidatorWithDefault tool we use in ODR, OPR, caver, etc. to automatically fill in defaults before validating the schema. then you can mark any field with a default as required and avoid messing around with get() and whatnot

Originally posted by @duncathan in #110 (review)

Additionally we shouldn't use string annotations of the explicit type, but instead use typing_extensions.Self.

[Miepee]

We should probably address the snake case before releasing 1.0.0