Tarred dataset support for audio classification models
This pull request **introduces 4 alerts** when merging d616be61a367dbac439f7a42e93a8e2638d23806 into 8c6152787e1eae5c6b23677df1be47041efe2d61 - [view on LGTM.com](https://lgtm.com/projects/g/NVIDIA/NeMo/rev/pr-7804a833bde0dad8ce222e13d982fae64a3c4981)

**new alerts:**

* 4 for Unused import This pull request **introduces 5 alerts** when merging 00e18b6ff8c903396f82ecfb058f5e7a873ddab6 into c6b90b3dd1321b3e95df8f91b89f55326d52a81c - [view on LGTM.com](https://lgtm.com/projects/g/NVIDIA/NeMo/rev/pr-313d01c6b288c870d3097f6bb5e0cce61a42eb99)

**new alerts:**

* 5 for Unused import
- [x] Refactor classification models and label models in audio_to_label 
- [x] Add support for tarred dataset for audio_to_label
- [x] Update classification models
- [x] Update VAD inference (should belong to Speaker Diarization pipelines PR but need to be used here)
- [x] Update training script, config, and instructions to use tarred dataset and improve consistency
- [x] Update converting_to_tarred_dataset script to support label models
- [x] Upload test data
- [x] Add test script
- [x] Ok a new one. enable using the duplicate name for tarred dataloader. (webdataset doesn't allow it) 
       Will try some hacky ways and discuss with people about a cleaner / long-term way after break. 

Updates for label_models will be in another PR 🚢    basically add the tarred option to the configs files.
