Add type hinting for Python SDK

[HarukaMa]

Add type hinting for the current available methods.

Type hinting helps SDK users and static type checkers to know the expected arguments and their expected types for methods, as native extensions don't expose them.

It looks like this after adding the type hinting:

(The docstring comes directly from the Rust code as PyO3 correctly stored them in the extension)

This PR is based on the #17, as the methods here currently are strictly ordered like the Rust code.

[kpp]

Constructors and dunder methods are not covered. However I am not a Python developer, I don't know how it can affect the experience.

[HarukaMa]

Most dunder methods should have their definitions in base types, like

class object:
	...
	def __eq__(self, __o: object) -> bool: ...

which can be found in the typeshed repo. Redefining them to stricter types won't actually work for static type checkers.

As for constructors, it seems only Account and PrivateKey have it defined and both are just def __new__(cls) -> Self, so it should work fine.

[kpp]

This PR is replaced by #22