Update plugin manager and built-in plugins to prioritize CallbackContext. Keep InvocationContext access for legacy plugins with adapter. Change callback docs/tests to cover the new context.
PiperOrigin-RevId: 818798087
This CL add new callbacks in plugin system:
- `on_tool_error_callback`
- `on_model_error_callback`
This allow the user to create plugins that can handle errors.
PiperOrigin-RevId: 786469646