Improve docstrings and type hints in scheduling_amused.py (#12623)
* Improve docstrings and type hints in scheduling_amused.py
- Add complete type hints for helper functions (gumbel_noise, mask_by_random_topk)
- Enhance AmusedSchedulerOutput with proper Optional typing
- Add comprehensive docstrings for AmusedScheduler class
- Improve __init__, set_timesteps, step, and add_noise methods
- Fix type hints to match documentation conventions
- All changes follow project standards from issue #9567
* Enhance type hints and docstrings in scheduling_amused.py
- Update type hints for `prev_sample` and `pred_original_sample` in `AmusedSchedulerOutput` to reflect their tensor types.
- Improve docstring for `gumbel_noise` to specify the output tensor's dtype and device.
- Refine `AmusedScheduler` class documentation, including detailed descriptions of the masking schedule and temperature parameters.
- Adjust type hints in `set_timesteps` and `step` methods for better clarity and consistency.
* Apply review feedback on scheduling_amused.py
- Replace generic [Amused] reference with specific [`AmusedPipeline`] reference for consistency with project documentation conventions