Data Simulator
# What does this PR do ?

Adds a multispeaker audio session simulator and corresponding documentation and tutorials.

Collections: ASR, Tools

# Changelog 
- Adds data simulator
- Adds a manifest_utils file and restructures speaker_utils
- Adds config files for simulating data as well as a tutorial and documentation

# 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?
- [ 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
- [ x] 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.
