Update dependencies and improve various functionalities

- Bump Gradle to 8.5 and adjust related configs.
- Upgrade from JDK 17 to JDK 21.
- Replace deprecated methods with modern equivalents (`withDisplayName` -> `withCustomName`).
- Refactor and simplify event handling (e.g., PlayerLoginEvent -> AsyncPlayerConfigurationEvent).
- Fix minor issues with player and inventory handling.
- Improve Gradle startup scripts for better compatibility.
- Transition plugin handling from deprecated to current class references.
- General cleanup and code modernization.

src/main/java/eu/mhsl/craftattack/worldmuseum/items/Items.java

@@ -12,47 +12,47 @@ import java.util.function.Consumer;
 
 public enum Items {
     HUB(
-            ItemStack
-                    .of(Material.IRON_DOOR)
-                    .withDisplayName(
-                            Component
-                                    .text("Zurück zur Überischt")
-                                    .color(NamedTextColor.GOLD)
-                    ),
-            player -> new VoidWorld().movePlayer(player)
+        ItemStack
+            .of(Material.IRON_DOOR)
+            .withCustomName(
+                Component
+                    .text("Zurück zur Überischt")
+                    .color(NamedTextColor.GOLD)
+            ),
+        player -> new VoidWorld().movePlayer(player)
     ),
 
     SPAWN(
-            ItemStack
-                    .of(Material.TARGET)
-                    .withDisplayName(
-                            Component
-                                    .text("Zum Spawn")
-                                    .color(NamedTextColor.GOLD)
-                    ),
-            SpawnCommand::teleportToSpawn
+        ItemStack
+            .of(Material.TARGET)
+            .withCustomName(
+                Component
+                    .text("Zum Spawn")
+                    .color(NamedTextColor.GOLD)
+            ),
+        SpawnCommand::teleportToSpawn
     ),
 
     MORE_SPEED(
-            ItemStack
-                    .of(Material.FEATHER)
-                    .withDisplayName(
-                            Component
-                                    .text("Schneller fliegen")
-                                    .color(NamedTextColor.AQUA)
-                    ),
-            player -> player.updateFlyingSpeed(0.05f)
+        ItemStack
+            .of(Material.FEATHER)
+            .withCustomName(
+                Component
+                    .text("Schneller fliegen")
+                    .color(NamedTextColor.AQUA)
+            ),
+    player -> player.updateFlyingSpeed(0.05f)
     ),
 
     LESS_SPEED(
-            ItemStack
-                    .of(Material.ANVIL)
-                    .withDisplayName(
-                            Component
-                                    .text("Langsamer fliegen")
-                                    .color(NamedTextColor.AQUA)
-                    ),
-            player -> player.updateFlyingSpeed(-0.05f)
+        ItemStack
+            .of(Material.ANVIL)
+            .withCustomName(
+                Component
+                    .text("Langsamer fliegen")
+                    .color(NamedTextColor.AQUA)
+            ),
+    player -> player.updateFlyingSpeed(-0.05f)
     );