* [feat] add KVAE-Audio autoencoder
* [fix] non-contiguous tensor into in_proj in AutoencoderKLKVAEAudio
* [chore] sync KVAE-Audio with upstream test and annotation changes
* [refactor] dedicated attention class and processor for AutoencoderKLKVAEAudio
* [refactor] remove the runtime sample_rate argument from AutoencoderKLKVAEAudio
* [refactor] always apply attention in AutoencoderKLKVAEAudio, drop use_attn
* [refactor] drop the derived latent_dim default from AutoencoderKLKVAEAudio
* [docs] fix encoder_rates docstring in AutoencoderKLKVAEAudio
* [refactor] rename Snake1d to KVAEAudioSnake1d in AutoencoderKLKVAEAudio
* [tests] skip layerwise casting training for AutoencoderKLKVAEAudio
