Use pydantic models to represent minecraft-data

[ItsDrike]

Addresses: #6

This PR moves away from using simple dict objects in favor of custom typed pydantic V2 models. This provides us with validation that the individual instances each follow the expected structure (which was designed based on the JSON schemas), and allows users to rely on the auto-completion features of their editor to get the data they're interested in.

This also remaps all camelCase fields to snake_case to follow idiomatic python conventions.

Warning

This is a breaking change, since:

• The load_common_data now returns a custom CommonData object, instead of a dict.
• The load_version now returns a custom VersionData object, instead of a dict.

The custom objects are not backwards compatible with dict (No __getitem__ support, camelCase fields were converted to snake_case)

This PR also introduces 2 new runtime dependencies:

• pydantic (for the model classes with automated conversion from a dict and field validations)
• eval_type_backport (to allow using modern type annotations with pydantic fields)