refactor: Use stream composition for firing field guns

It may be possible to optimize this further if it can be assumed that
all CI attacks either have the infantry flag or are field guns, but I've
settled for replicating the previous logic for now.

Author: Saklad5

megamek/src/megamek/common/actions/WeaponAttackAction.java

@@ -2168,21 +2168,23 @@ private static String toHitIsImpossible(Game game, Entity ae, int attackerId, Ta
                     return Messages.getString("WeaponAttackAction.CantMoveAndFieldGun");
                 }
                 // check for mixing infantry and field gun attacks
-                for (Enumeration<EntityAction> i = game.getActions(); i.hasMoreElements();) {
-                    EntityAction ea = i.nextElement();
-                    if (!(ea instanceof WeaponAttackAction)) {
-                        continue;
-                    }
-                    final WeaponAttackAction prevAttack = (WeaponAttackAction) ea;
-                    if (prevAttack.getEntityId() == attackerId) {
-                        Mounted prevWeapon = ae.getEquipment(prevAttack.getWeaponId());
-                        if ((prevWeapon.getType().hasFlag(WeaponType.F_INFANTRY)
-                                && (weapon.getLocation() == Infantry.LOC_FIELD_GUNS))
-                                || (weapon.getType().hasFlag(WeaponType.F_INFANTRY)
-                                        && (prevWeapon.getLocation() == Infantry.LOC_FIELD_GUNS))) {
-                            return Messages.getString("WeaponAttackAction.FieldGunOrSAOnly");
-                        }
-                    }
+                if (game.getActionsVector().stream()
+                    .filter(WeaponAttackAction.class::isInstance)
+                    .map(WeaponAttackAction.class::cast)
+                    .filter(prevAttack -> prevAttack.getEntityId() == attackerId)
+                    .map(prevAttack -> ae.getEquipment(prevAttack.getWeaponId()))
+                    .anyMatch(prevWeapon ->
+                        (
+                            prevWeapon.getType().hasFlag(WeaponType.F_INFANTRY)
+                                && weapon.getLocation() == Infantry.LOC_FIELD_GUNS
+                        )
+                        || (
+                            prevWeapon.getLocation() == Infantry.LOC_FIELD_GUNS
+                                && weapon.getType().hasFlag(WeaponType.F_INFANTRY)
+                        )
+                    )
+                ) {
+                    return Messages.getString("WeaponAttackAction.FieldGunOrSAOnly");
                 }
             }