[speechx]refactor linear feature:unify vector & remove redundant function & add remained_wav cache shift wav

[vec][search] update search demo README

[Doc] supplement note

[TTS]add license and reference for some models

[speechx] fix nnet itf header

[speechx] Frontend refactor

[speechx] refactor audio/data/feature cache

[Audio][docs]Update README.md

Update readme in docs. test=doc

[TTS]Cnn decoder

[speechx]fix the crush of example/decoder/run.sh