nixos/dnscrypt-proxy2: init

This removes the original dnscrypt-proxy module as well.

Co-authored-by: Atemu <atemu.main@gmail.com>
Co-authored-by: Silvan Mosberger <contact@infinisil.com>
Co-authored-by: ryneeverett <ryneeverett@gmail.com>
Co-authored-by: worldofpeace <worldofpeace@protonmail.ch>