Tree-like objective node structure (#7152)

* overall structure

* overall layout

* field interpreter

* less bloated UI

* scroll pan't

* strip off the 'Marker' suffix

* e

* all (hopefully all...) interpreters finished.

* onset

* two, four

* i don't understand how icon mappings work.

* separate remover and indexer

* some cleanups

* untested mobile support

* contrib

* ok anuke

* fix conflicts 2

* hidden

core/src/mindustry/graphics/OverlayRenderer.java

@@ -113,13 +113,10 @@ public class OverlayRenderer{
             }
         }
 
-        //draw objective markers, if any
-        if(state.rules.objectives.size > 0){
-            var first = state.rules.objectives.first();
-            for(var marker : first.markers){
-                marker.draw();
-            }
-        }
+        //draw objective markers
+        state.rules.objectives.eachRunning(obj -> {
+            for(var marker : obj.markers) marker.draw();
+        });
 
         if(player.dead()) return; //dead players don't draw