Expose evaluate() for user-provided params

1) Evaluate button is removed, but the underlying routine is still exposed in our Python API. Providing a bit of example code that users can copy+paste to evaluate their tweaks would be a nice gesture for affected users.

_Originally posted by @dae in https://github.com/ankitects/anki/issues/3962#issuecomment-2927298959_

- Currently, it appears we're only exposing the new implementation, and not the old one.
- Some sample code for users would be good