Add WorldBeforeLoadEvent and WorldEndLoadEvent (#7523)

* Add `WorldBeforeLoadEvent` and `WorldEndLoadEvent`

* rename

core/src/mindustry/core/World.java

@@ -202,6 +202,7 @@ public class World{
      */
     public void beginMapLoad(){
         generating = true;
+        Events.fire(new WorldLoadBeginEvent());
     }
 
     /**
@@ -209,6 +210,7 @@ public class World{
      * A WorldLoadEvent will be fire.
      */
     public void endMapLoad(){
+        Events.fire(new WorldLoadEndEvent());
 
         for(Tile tile : tiles){
             //remove legacy blocks; they need to stop existing

core/src/mindustry/game/EventType.java

@@ -77,8 +77,13 @@ public class EventType{
     public static class MusicRegisterEvent{}
     /** Called *after* all the modded files have been added into Vars.tree */
     public static class FileTreeInitEvent{}
-    /** Called when a game begins and the world tiles are loaded. Entities are not yet loaded at this stage.  */
+
+    /** Called when a game begins and the world tiles are loaded, just set `generating = false`. Entities are not yet loaded at this stage. */
     public static class WorldLoadEvent{}
+    /** Called when the world begin to load, just set `generating = true`. */
+    public static class WorldLoadBeginEvent{}
+    /** Called when a game begins and the world tiles are initiated. About to updates tile proximity and sets up physics for the world(Before WorldLoadEvent) */
+    public static class WorldLoadEndEvent{}
 
     public static class SaveLoadEvent{
         public final boolean isMap;