DiffSinger: support different dictionaries for Chinese, Japanese and Cantonese

[oxygen-dioxide]

• DiffSinger voicebanks can use different dictionaries for Chinese (dsdict-zh.yaml), Japanese (dsdict-ja.yaml) and Cantonese (dsdict-zh-yue.yaml). For example, DiffSinger Chinese phonemizer tries to load dsdict-zh.yaml first. If dsdict-zh.yaml isn't found, it will load dsdict.yaml as before. This will make it easier to develop multilingual voicebanks.
  • This change doesn't affect existing voicebanks.
• Add DiffSinger Japanese phonemizer (DIFFS JA). Currently the only difference between DIFFS JA and DIFFS is that DIFFS JA tries to load dsdict-ja.yaml before loading dsdict.yaml.
• Moved diffsinger phonemizer code to a subfolder.

[stakira]

conflict