Add new augmentations: lowpass filtering, lossy compression (opus/mp3/vorbis)

[racoiaws]

This PR adds two operations on Cuts/Recordings and corresponding randomized CutSet transforms

1. Lowpass filtering
2. In-memory lossy compression (with immediate decoding back to raw waveform)

Both would be useful for training robust ASR models, speech enhancement models, etc.

TODO

• tests
• docstrings for new methods in lhotse.audio.recording.Recording