networkmanager service: use resolved if enabled

[florianjacob]

Motivation for this change

This allows /etc/resolv.conf and dns resolution in general to be managed by systemd-resolved while still being able to use NetworkManager for the actual networking.

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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[0xABAB]

@7c6f434c Can you merge this?

[7c6f434c]

Ah, that's a service, I usually ignore these (for obvious reasons like not running systemd). But seems simple and clear enough, I agree.

[florianjacob]

@7c6f434c @0xABAB Thank you! 😄