Add chat template support for llama-cli (#8068)

* add chat template support for llama-cli

* add help message

* server: simplify format_chat

* more consistent naming

* improve

* add llama_chat_format_example

* fix server

* code style

* code style

* Update examples/main/main.cpp

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

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