[Feature] Use pydantic instead of raw parsing

[manchenkoff]

What is a problem? A lot of inappropriate code for parsing key-value to data classes, like extract_attrs or extract_typed_props

Describe the solution you'd like Use Pydantic with automatic resolving and type casting methods

Describe alternatives you've considered Nothing

Additional context Nothing

[rafalkrupinski]

aiopenapi3 has quite good OAD model for all 3 versions (swagger 2, OAI 3 & 3.1), written in Pydantic and on MIT license. The model has some project-specific code, but surely cleaning it would be less work than starting from scratch.