Don't send UUID cape or ear requests if player is an NPC

Addresses #2722

core/src/main/java/org/geysermc/geyser/skin/SkinProvider.java

@@ -56,6 +56,7 @@ import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.*;
 import java.util.concurrent.*;
+import java.util.function.Predicate;
 
 public class SkinProvider {
     public static final boolean ALLOW_THIRD_PARTY_CAPES = GeyserImpl.getInstance().getConfig().isAllowThirdPartyCapes();
@@ -83,6 +84,12 @@ public class SkinProvider {
 
     private static final Map<UUID, SkinGeometry> cachedGeometry = new ConcurrentHashMap<>();
 
+    /**
+     * Citizens NPCs use UUID version 2, while legitimate Minecraft players use version 4, and
+     * offline mode players use version 3.
+     */
+    public static final Predicate<UUID> IS_NPC = uuid -> uuid.version() == 2;
+
     public static final boolean ALLOW_THIRD_PARTY_EARS = GeyserImpl.getInstance().getConfig().isAllowThirdPartyEars();
     public static final String EARS_GEOMETRY;
     public static final String EARS_GEOMETRY_SLIM;
@@ -293,6 +300,10 @@ public class SkinProvider {
                                                                 String username, boolean newThread) {
         if (officialCape.isFailed() && ALLOW_THIRD_PARTY_CAPES) {
             for (CapeProvider provider : CapeProvider.VALUES) {
+                if (provider.type != CapeUrlType.USERNAME && IS_NPC.test(playerId)) {
+                    continue;
+                }
+
                 Cape cape1 = getOrDefault(
                         requestCape(provider.getUrlFor(playerId, username), provider, newThread),
                         EMPTY_CAPE, 4
@@ -330,6 +341,10 @@ public class SkinProvider {
      */
     public static CompletableFuture<Skin> requestUnofficialEars(Skin officialSkin, UUID playerId, String username, boolean newThread) {
         for (EarsProvider provider : EarsProvider.VALUES) {
+            if (provider.type != CapeUrlType.USERNAME && IS_NPC.test(playerId)) {
+                continue;
+            }
+
             Skin skin1 = getOrDefault(
                     requestEars(provider.getUrlFor(playerId, username), newThread, officialSkin),
                     officialSkin, 4