Add a function that writes cluster label in diarization pipeline
# What does this PR do ?

This PR adds a function that writes cluster label. This cluster label (speaker label for each segment) is needed to provide estimated segment label for overlap-aware diarization module or target-speaker ASR.

**Collection**: asr (but actually speaker_tasks)

# Changelog 
- Removed unnecessary line in speaker_utils.py
- Added a line that adds segment info and cluster label
- Added lines that write files to speaker_outputs.

# Usage
Please refer to [Diarization docs](https://docs.nvidia.com/deeplearning/nemo/user-guide/docs/en/main/asr/speaker_diarization/datasets.html)

# 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)
- [ ] Did you write any new necessary tests?
- [ ] 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

## 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.

