Support transcoding audio formats when saving tarred datasets (FLAC, OPUS)
jenkins jenkins
# What does this PR do ?

Supports saving audio into compressed formats when creating a tarred dataset.

**Collection**: Any speech collection

# Changelog 
- Add option `--force_codec [name]` to `scripts/speech_recognition/convert_to_tarred_audio_dataset.py` 
- Acceptable values: `wav`, `flac`, `opus`, possibly others supported by libsndfile
- When `--force_codec` is provided, and the audio file extension is different than codec's name, we'll read the audio and transcode it in memory, then save to tar; otherwise the existing code path is selected
- Change the default to save files as `opus`. Soundfile uses 28kbps for OPUS which is adequate for podcasts/audiobooks according to https://wiki.xiph.org/Opus_Recommended_Settings -- the result is ~17x smaller than FLAC and 26x smaller than WAVE (current default). 

# Usage

```bash
python scripts/speech_recognition/convert_to_tarred_audio_dataset.py --manifest_path nemo_manifest.json --num_shards 4 --force_codec opus --workers 4 --max_duration 30
```

# Jenkins CI
To run Jenkins, a NeMo User with write access must comment `jenkins` on the PR.

# 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)
