vocab : refactor tokenizer to reduce init overhead (#9449)

* refactor tokenizer

* llama : make llm_tokenizer more private

ggml-ci

* refactor tokenizer

* refactor tokenizer

* llama : make llm_tokenizer more private

ggml-ci

* remove unused files

* remove unused fileds to avoid unused filed build error

* avoid symbol link error

* Update src/llama.cpp

* Update src/llama.cpp

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Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>