Auto convert tekken.json (#42299)
* auto convert tekken.json
* fix conversion
* simplify
* nit
* model info based on the fly fix
* up
* last nit
* fixup
* call it fix mistral regex
* fix behaviour for local or only tok is saved
* style
* rm comment at wrong palce
* fix escaping
* style
* fix backend tokenizer attr to _tokenizer
* update
* up
* update
* fix the last red tests
