improve nodeinfo

- enable usage outside of secure-node.nix
- use json as the output format
- show ports
- also show local addresses, which is particularly useful when
  netns-isolation is enabled
- only show enabled services

test/tests.nix

@@ -68,6 +68,8 @@ let testEnv = rec {
         '';
       };
 
+      tests.nodeinfo = config.nix-bitcoin.nodeinfo.enable;
+
       tests.backups = cfg.backups.enable;
 
       # To test that unused secrets are made inaccessible by 'setup-secrets'
@@ -119,6 +121,8 @@ let testEnv = rec {
       services.joinmarket.enable = true;
       services.backups.enable = true;
 
+      nix-bitcoin.nodeinfo.enable = true;
+
       services.hardware-wallets = {
         trezor = true;
         ledger = true;