On data preprocessing enhancements

[Yocauu]

Observing that there is no mature data preprocessing in this project, which directly uses raw data for training, we propose to add data preprocessing

[Yanyaodong]

It is found that individual methods in this set of neural networks, such as VQ-VAE, can use VQ-VAE2 to replace existing techniques

[joezzzzz7]

Through research, there are many possible methods in the vocoder section. We try to replace the original hifi-gan method with diffwave method which has better network structure to see if it can improve the quality of the generated audio.

[ceshizxz]

The project currently does not have a mature separate integrated test document and needs to be improved in the future.