common : refactor arg parser (#9308)

* (wip) argparser v3

* migrated

* add test

* handle env

* fix linux build

* add export-docs example

* fix build (2)

* skip build test-arg-parser on windows

* update server docs

* bring back missing --alias

* bring back --n-predict

* clarify test-arg-parser

* small correction

* add comments

* fix args with 2 values

* refine example-specific args

* no more lamba capture

Co-authored-by: slaren@users.noreply.github.com

* params.sparams

* optimize more

* export-docs --> gen-docs