[ASR] Generate multichannel noise
# What does this PR do ?

This PR adds tools for generating multi-channel microphone signal approximately matching the desired spatial coherence

**Collection**: ASR

# Changelog 
- Adds functions for generating an approximate noise field
- Unit tests for spatial coherence calculation and noise generation

# Usage

```python
noise_field = generate_approximate_noise_field(mic_positions, noise_signal, sample_rate)
```

where `mic_positions` are positions of the `M` microphones in 3D Cartesian coordinates, `noise_signal` is an `M`-channel noise signal, where channels are statistically independent, sampled at `sample_rate` Hz. Currently, only `spherical` noise field is supported.

# 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?
- [ ] 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

## 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
n/a
