sks and pgpkeyserver-lite modules: init (#27515)

* modules sks and pgpkeyserver-lite:
  runs the sks keyserver with optional nginx proxy for webgui.
* Add calbrecht to maintainers
* module sks: fix default hkpAddress value
* module pgpkeyserver-lite: make hkpAddress a string type option
  and use (builtins.head services.sks.hkpAddress) as default value
* module sks: remove leftover service dependencies