Add missing 'type', 'defaultText' and 'literalExample' in module definitions

- add missing types in module definitions
- add missing 'defaultText' in module definitions
- wrap example with 'literalExample' where necessary in module definitions

nixos/modules/services/logging/logstash.nix

@@ -33,6 +33,7 @@ in
       package = mkOption {
         type = types.package;
         default = pkgs.logstash;
+        defaultText = "pkgs.logstash";
         example = literalExample "pkgs.logstash";
         description = "Logstash package to use.";
       };
@@ -84,7 +85,7 @@ in
         type = types.lines;
         default = ''stdin { type => "example" }'';
         description = "Logstash input configuration.";
-        example = literalExample ''
+        example = ''
           # Read from journal
           pipe {
             command => "''${pkgs.systemd}/bin/journalctl -f -o json"