Fix failing speaker counting for short audio samples
# What does this PR do ?

From the previous PR (https://github.com/NVIDIA/NeMo/pull/5191/files), 
Speaker clustering code is now fully jit-scriptable, but speaker counting algorithm for 
short audio sample (less than 40s) was dropped.

In this PR, we are adding `getEnhancedSpeakerCount` function back and now tutorial notebooks are working correctly.

**Collection**: [Note which collection this PR will affect]

# Changelog 

- added `getEnhancedSpeakerCount` function back that handles very short audio samples
- checked the python and torch.jit.script modes

# Usage
* You can potentially add a usage example below

```python
  python neural_diarizer/multiscale_diar_decoder_infer.py \
    diarizer.manifest_filepath=<path to manifest file> \
    diarizer.out_dir='demo_output' \
    diarizer.speaker_embeddings.parameters.save_embeddings=False \
    diarizer.vad.model_path=<pretrained model name or path to .nemo> \
    diarizer.speaker_embeddings.model_path=<pretrained speaker embedding model name or path to .nemo> \
    diarizer.msdd_model.model_path=<pretrained MSDD model name or path .nemo> \
```

# Before your PR is "Ready for review"
**Pre checks**:
- [x] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [x] Did you write any new necessary tests?
- [x] Did you add or update any necessary documentation?
- [ ] Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  - [ ] Reviewer: Does the PR have correct import guards for all optional libraries?
  
**PR Type**:
- [x] New Feature
- [ ] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?

Anyone in the community is free to review the PR once the checks have passed. 
[Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md) contains specific people who can review PRs to various areas.

# Additional Information
* Related to # (issue)
