Update Chinese-Japanese bilingual model path to be espnet/mixdata_svs_visinger2_spkemb_lang_pretrained

Update Japanese text preprocessing and formatting to support natural Japanese text input without spaces between characters

Continue:

Refactor svs_inference and related functions; Bug fixes and code cleanup

Push demo

syntax updates

Co-authored-by: Yiwen Zhao <Tsukasane@users.noreply.github.com> & Jionghao