Audiotree

* `jit` has been removed in most places. We encourage users to jit as late as possible, and DAC-JAX demonstrates this.
* New class: `AudioDataBalancedDataset`, which is a grain Dataset, **not a Data Source**.
* `AudioTree` has a `.latents` property.
* New transform: `NeuralLatentEncodeTransform`.
* Class `NeuralAudioCodecEncodeTransform` has been adjusted. The arg is now `encoder_fn` and it takes an `AudioTree` instead of an audio data array.
* In an `AudioTree`'s metadata, the offset and duration will now be 1D arrays instead of 0D arrays.
* `cpu` has a kwarg has been removed in most places. You should think of AudioTrees as existing on CPU by default. If you pass them to a jitted function then they will be put on device.
* In, `AudioDataSimpleSource` and `AudioDataBalancedSource`, `num_steps` arg is now `num_records`. Also `._filepaths` property is now `.filepaths`.

**Breaking changes:**
* `SaliencyParams` has moved from `audiotree.datasources.SaliencyParams` to `audiotree.SaliencyParams`

Updates:
The code has been tested with device parallel sharding.
See the recent updates to [DAC-JAX](https://github.com/DBraun/DAC-JAX/blob/main/scripts/input_pipeline.py).
SaliencyParams has a new `search_function` parameter.
The two valid strings are `SaliencyParams.search_uniform` and `SaliencyParams.search_early_bias`.
You can also plug in your own Callable function.

First release.