Improve inference from return type annotations in completer

[krassowski]

Addresses the issue of non-jedi completer not picking type annotations for __init__() brought up in #14336

Follow-up to #14185

Supports:

• Annotated
• AnyStr
• Literal
• LiteralString
• NewType
• Optional
• Protocol
• Self
• TypeAliasType (type keyword in Python 3.12+)
• TypedDict
• TypeGuard
• Union

Limitations:

• no type narrowing: ambiguous return types from Union, and Optional will always return all possible values
• generics (TypeVar and Generic) are not support (except for AnyStr)
• old style TypeAlias (deprecated in Python 3.12) is not supported