Replace more PacketType#prepare usage

Also mark methods as internal

api/src/main/java/com/github/retrooper/packetevents/protocol/packettype/PacketType.java

@@ -438,6 +438,10 @@ public final class PacketType {
             ClientVersion.V_1_21_6,
             ClientVersion.V_1_21_9);
 
+    private PacketType() {
+    }
+
+    @ApiStatus.Internal
     public static void prepare() {
         if (PREPARED) {
             return;
@@ -457,6 +461,7 @@ public final class PacketType {
         }
     }
 
+    @ApiStatus.Internal
     public static boolean isPrepared() {
         return PREPARED;
     }

api/src/test/java/com/github/retrooper/packetevents/test/base/TestPacketEventsBuilder.java

@@ -97,9 +97,7 @@ public class TestPacketEventsBuilder {
                     PacketEvents.SERVER_CHANNEL_HANDLER_NAME = "pe-connection-initializer-" + id;
                     PacketEvents.TIMEOUT_HANDLER_NAME = "pe-timeout-handler-" + id;
 
-                    if (!PacketType.isPrepared()) {
-                        PacketType.prepare();
-                    }
+                    PacketType.prepare();
 
                     loaded = true;
                 }

spigot/src/main/java/io/github/retrooper/packetevents/factory/spigot/SpigotPacketEventsBuilder.java

@@ -114,9 +114,7 @@ public class SpigotPacketEventsBuilder {
                         throw new IllegalStateException(ex);
                     }
 
-                    if (!PacketType.isPrepared()) {
-                        PacketType.prepare();
-                    }
+                    PacketType.prepare();
 
                     //Server hasn't bound to the port yet.
                     lateBind = !injector.isServerBound();

sponge/src/main/java/io/github/retrooper/packetevents/sponge/factory/SpongePacketEventsBuilder.java

@@ -106,9 +106,7 @@ public class SpongePacketEventsBuilder {
                     throw new IllegalStateException(ex);
                 }
 
-                if (!PacketType.isPrepared()) {
-                    PacketType.prepare();
-                }
+                PacketType.prepare();
 
                 // Server hasn't bound to the port yet.
                 lateBind = !injector.isServerBound();