[ASR] AudioToAudio datasets and related test
# What does this PR do ?

This is a draft PR of datasets for different audio-to-audio tasks.

**Datasets**

- `BaseAudioDataset`: Abstract base class.
- `AudioToTargetDataset`: A dataset for audio-to-audio tasks where the goal is to use an input signal to recover the corresponding target signal.
- `AudioToTargetWithReferenceDataset`: A dataset for audio-to-audio tasks where the goal is to use an input signal to recover the corresponding target signal and an additional reference signal is available.
- `AudioToTargetWithEmbeddingDataset`: A dataset for audio-to-audio tasks where the goal is to use an input signal to recover the corresponding target signal and an additional embedding signal. It is assumed that the embedding is in a form of a vector.

**Tests**

Multiple tests are implemented in `test_asr_datasets.py` in class `TestAudioDatasets`. These tests include

- `test_audio_to_target_dataset`: multiple tests for `AudioToTargetDataset`
- `test_audio_to_target_dataset_with_target_list`: tests specifically a scenario where target is provides as a list of files
- `test_audio_to_target_with_reference_dataset`: tests for `AudioToTargetWithReferenceDataset`
- `test_audio_to_target_with_embedding_dataset`: tests for `AudioToTargetWithEmbeddingDataset`

Tests can be started using the following command
```
pytest tests/collections/asr/test_asr_datasets.py::TestAudioDatasets
```

**Collection**: ASR

# Changelog 
- Added datasets in `audio_to_audio.py`
- Added unit tests in `test_asr_datasets.py` and `test_audio_utils.py`
- Added an option in `AudioSegment. segment_from_file` to use a fixed offset

# Usage

Usage is illustrated in unit tests, which can be executed using

```python
pytest tests/collections/asr/test_asr_datasets.py::TestAudioDatasets
```

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**PR Type**:
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- [ ] Bugfix
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# Additional Information
* Related to # (issue)
