audio_utils improvements (#21998)
* silly change to allow making a PR
* clean up doc comments
* simplify hertz_to_mel and mel_to_hertz
* fixup
* clean up power_to_db
* also add amplitude_to_db
* move functions
* clean up mel_filter_bank
* fixup
* credit librosa & torchaudio authors
* add unit tests
* tests for power_to_db and amplitude_to_db
* add mel_filter_bank tests
* rewrite STFT
* add convenience spectrogram function
* missing transpose
* fewer transposes
* add integration test to M-CTC-T
* frame length can be either window or FFT length
* rewrite stft API
* add preemphasis coefficient
* move argument
* add log option to spectrogram
* replace M-CTC-T feature extractor
* fix api thing
* replace whisper STFT
* replace whisper mel filters
* replace tvlt's stft
* allow alternate window names
* replace speecht5 stft
* fixup
* fix integration tests
* fix doc comments
* remove manual FFT length calculation
* fix docs
* go away, deprecation warnings
* combine everything into spectrogram function
* add deprecated functions back
* fixup
