[Py] Add EmbedderReference dataclass

[MengqinShen]

Is your feature request related to a problem? Please describe.
Python already has a basic embedder reference system, but it's less sophisticated than JavaScript.

Describe the solution you'd like
Python equivalent of the JS EmbedderReference interface with fields: name, config_schema, info, config, version

Additional context
Reference: js/ai/src/embedder.ts:319-327 (the JS interface definition)