args: add env vars for temperature, top-p, min-p and penalties (#27380)
Allow configuring --temp, --top-p, --min-p, --repeat-penalty,
--presence-penalty and --frequency-penalty via LLAMA_ARG_* so
llama-server can be fully controlled from an EnvironmentFile
(e.g. systemd on Debian).
Use `llama-gen-docs` to regenerate the readme files.