common : allow caller to handle help/argument exceptions (#3715)

common : allow caller to handle help/argument exceptions (#3715)

* Allow caller to handle help/argument exceptions

* Prepend newline to usage output

* Add new gpt_params_parse_ex function to hide arg-parse impl

* Fix issue blocking success case

* exit instead of returning false

* Update common/common.h

Co-authored-by: Georgi Gerganov <redacted>
* Update common/common.cpp

Co-authored-by: Georgi Gerganov <redacted>
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Co-authored-by: Georgi Gerganov <redacted>