zlib: move, rename, document internal params() cb

Give the callback a more specific name, explain what it does
and why it is necessary, and move it to a location much closer
to its use site.

PR-URL: https://github.com/nodejs/node/pull/23187


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>