PointLaserBulletType support for Weapons (#9331)

* PointLaserBulletType support for Weapons

I hate adding more fields to Weapon, but oh well. It's the price to pay when the behavior of what should be spread across multiple classes is compacted into a single class.

* Fix several problems

core/src/mindustry/entities/units/WeaponMount.java

@@ -40,6 +40,8 @@ public class WeaponMount{
     public int totalShots;
     /** counter for which barrel bullets have been fired from; used for alternating patterns */
     public int barrelCounter;
+    /** Last aim length of weapon. Only used for point lasers. */
+    public float lastLength;
     /** current bullet for continuous weapons */
     public @Nullable Bullet bullet;
     /** sound loop for continuous weapons */