Add events to support scene group substitution (#2413)

* Add events to support scene group substitution

* make event members private with getter/setter

* delete stray unused var

src/main/java/emu/grasscutter/server/event/game/SceneMetaLoadEvent.java

@@ -0,0 +1,17 @@
+package emu.grasscutter.server.event.game;
+
+import emu.grasscutter.game.world.Scene;
+import emu.grasscutter.server.event.types.ServerEvent;
+import lombok.*;
+
+@Getter
+public final class SceneMetaLoadEvent extends ServerEvent {
+    private Scene scene;
+    @Setter private boolean override;
+
+    public SceneMetaLoadEvent(Scene scene) {
+        super(Type.GAME);
+
+        this.scene = scene;
+    }
+}