Lhotse AudioToAudio dataset (supports ref recording and embedding)
~Note: requires some fixes in lhotse, will bump the requirements as soon as I release it.~ EDIT: done jenkins jenkins This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale. jenkins jenkins jenkins jenkins jenkins jenkins jenkins Everything passed in jenkins, merging
# What does this PR do ?

We're adding several features to enable audio-to-audio dataloading:
* Conversion script from NeMo audio-to-audio manifests to Lhotse format 
* Audio-to-audio Lhotse dataset (covers a2a, a2a with reference and a2a with embedding cases)
* Auto-supports Lhotse Shar (tarred) format for audio-to-audio
* Options to cut/truncate examples into smaller chunks on the fly

**Collection**: All speech collections

# Changelog 
* Conversion script from NeMo audio-to-audio manifests to Lhotse format 
* Audio-to-audio Lhotse dataset (covers a2a, a2a with reference and a2a with embedding cases)
* Auto-supports Lhotse Shar (tarred) format for audio-to-audio
* Options to cut/truncate examples into smaller chunks on the fly

# Usage

Generally the workflow to use this is as follows:

```bash
# First convert NeMo manifest to Lhotse:
python scripts/audio_to_audio/convert_nemo_to_lhotse.py \
  nemo_manifest.json \
  lhotse_manifest.jsonl.gz \
  -i input_filepath \
  -t target_filepath

# Then, convert to Lhotse Shar (tarred) format
# Meaning of args: 
#  -j4 is 4 jobs
# -s 100 is the shard size
# -c specifies custom fields we want to export and their format, see lhotse shar export --help
lhotse shar export \
  -j4 -v -s 100 \
  -a flac \
  -c target_recording:flac \
  lhotse.jsonl.gz \
  data_shar
```

Then you can instantiate the dataloader like the following:

```python
from omegaconf import OmegaConf
from nemo.collections.common.data.lhotse import get_lhotse_dataloader_from_config
from nemo.collections.asr.data.audio_to_audio_lhotse import LhotseAudioToTargetDataset

config = {
   'shar_path': 'data_shar',
   'sample_rate': 16000,
   'batch_duration': 100,
   'use_bucketing': True,
   'num_buckets': 2,
}

dl = get_lhotse_dataloader_from_config(
   OmegaConf.create(config), global_rank=0, world_size=1, dataset=LhotseAudioToTargetDataset()
)
```

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

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