ref!: Don't make generated types part of public api

[Luca Forstner (lforst)]

Ref SDK-226

• Replace broad, backend-generated SDK types with smaller, explicit contracts, reducing the type complexity users’ editors and TypeScript compilers must process.
• Bundle only the runtime validators the SDK needs. Previously, importing generated schemas also pulled unrelated backend validators into client bundles.
• Simplify prompt and function types and remove internal cache-serialization methods from the public API, while preserving supported inputs and autocomplete.
• Keep generated definitions as compatibility references, with tests checking type compatibility, validation behavior, autocomplete, and their exclusion from production bundles. All 1,536 replay tests pass.

[Abhijeet Prasad (AbhiPrasad)]

there might be an easier way 👁️ https://github.com/braintrustdata/braintrust-sdk-python/tree/main/py/src/braintrust/api