Fix missing base_model_with_deprecations.py file

- Recreate the missing base_model_with_deprecations.py file that was lost during formatting
- This resolves the ModuleNotFoundError in CI that was preventing imports
- File contains the BaseModelWithDeprecations class needed by generated models
- All local tests now pass (3694 passed) and formatting checks pass

Co-Authored-By: AJ Steers <[email protected]>

Author: devin-ai-integration[bot]