Rewrite MessagingService message encoding, conform to new plugin message channel requirements

* This change isn't backwards compatible with previous builds, this version (& onwards) won't be able to "communicate" with old versions, and vice versa.

* MC 1.13 requires plugin message channel names to be namespaced, so 'lpuc' has been changed to 'luckperms:update'

* The channel names for Redis/Lily types have also changed, I've been wanting to change the encoded format to something a bit saner for a while, and this seemed like a good time. Changing the channel names a) keeps things consistent and b) means I don't have to worry about old versions interpreting the new format.

bungee/src/main/java/me/lucko/luckperms/bungee/messaging/BungeeMessenger.java

@@ -46,7 +46,7 @@ import javax.annotation.Nonnull;
  * An implementation of {@link Messenger} using the plugin messaging channels.
  */
 public class BungeeMessenger implements Messenger, Listener {
-    private static final String CHANNEL = "lpuc";
+    private static final String CHANNEL = "luckperms:update";
 
     private final LPBungeePlugin plugin;
     private final IncomingMessageConsumer consumer;

bungee/src/main/java/me/lucko/luckperms/bungee/messaging/RedisBungeeMessenger.java

@@ -43,7 +43,7 @@ import javax.annotation.Nonnull;
  * An implementation of {@link Messenger} using Redis, via RedisBungee's API.
  */
 public class RedisBungeeMessenger implements Messenger, Listener {
-    private static final String CHANNEL = "lpuc";
+    private static final String CHANNEL = "luckperms:update";
 
     private final LPBungeePlugin plugin;
     private final IncomingMessageConsumer consumer;