Multi shotgun fix (#8460)

* Multi-barrel shotgun fix

* multi-recoil support

* @Nullable for everything

core/src/mindustry/entities/pattern/ShootSpread.java

@@ -1,5 +1,7 @@
 package mindustry.entities.pattern;
 
+import arc.util.*;
+
 public class ShootSpread extends ShootPattern{
     /** spread between bullets, in degrees. */
     public float spread = 5f;
@@ -13,7 +15,7 @@ public class ShootSpread extends ShootPattern{
     }
 
     @Override
-    public void shoot(int totalShots, BulletHandler handler){
+    public void shoot(int totalShots, BulletHandler handler, @Nullable Runnable barrelIncrementer){
         for(int i = 0; i < shots; i++){
             float angleOffset = i * spread - (shots - 1) * spread / 2f;
             handler.shoot(0, 0, angleOffset, firstShotDelay + shotDelay * i);