Fix incorrect collision shape for hopper item suck

It shouldn't cost too much more to check the correct shape,
provided that it is cached and we use the overall AABB
to collect possible entities to check against.

The issues with the old check code is that it will use two
getEntitiesOfClass calls plus the addition of streams
_and_ the toAabbs() logic on VoxelShape. The new code
caches toAabbs, uses one getEntitiesOfClass call, and
does not use streams. Then compared to 1.12, we are
only performing two additional AABB checks per item.

patches/server/Optimize-Hoppers.patch

@@ -510,19 +510,38 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
                  flag = true;
              } else if (HopperBlockEntity.canMergeItems(itemstack1, stack)) {
 @@ -0,0 +0,0 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
+         // CraftBukkit end
      }
  
++    // Paper start - optimize hopper item suck in
++    static final AABB HOPPER_ITEM_SUCK_OVERALL = Hopper.SUCK.bounds();
++    static final AABB[] HOPPER_ITEM_SUCK_INDIVIDUAL = Hopper.SUCK.toAabbs().toArray(new AABB[0]);
++    // Paper end - optimize hopper item suck in
++
      public static List<ItemEntity> getItemsAtAndAbove(Level world, Hopper hopper) {
 -        return (List) hopper.getSuckShape().toAabbs().stream().flatMap((axisalignedbb) -> {
 -            return world.getEntitiesOfClass(ItemEntity.class, axisalignedbb.move(hopper.getLevelX() - 0.5D, hopper.getLevelY() - 0.5D, hopper.getLevelZ() - 0.5D), EntitySelector.ENTITY_STILL_ALIVE).stream();
 -        }).collect(Collectors.toList());
-+        // Paper start - Optimize item suck in. remove streams, restore 1.12 checks. Seriously checking the bowl?!
-+        double x = hopper.getLevelX();
-+        double y = hopper.getLevelY();
-+        double z = hopper.getLevelZ();
-+        AABB bb = new AABB(x - 0.5D, y, z - 0.5D, x + 0.5D, y + 1.5D, z + 0.5D);
-+        return world.getEntitiesOfClass(ItemEntity.class, bb, Entity::isAlive);
-+        // Paper end
++        // Paper start - optimize hopper item suck in
++        // eliminate multiple getEntitiesOfClass() but maintain the voxelshape collision by moving
++        // the individual AABB checks into the predicate
++        final double shiftX = hopper.getLevelX() - 0.5D;
++        final double shiftY = hopper.getLevelY() - 0.5D;
++        final double shiftZ = hopper.getLevelZ() - 0.5D;
++        return world.getEntitiesOfClass(ItemEntity.class, HOPPER_ITEM_SUCK_OVERALL.move(shiftX, shiftY, shiftZ), (final Entity entity) -> {
++            if (!entity.isAlive()) { // EntitySelector.ENTITY_STILL_ALIVE
++                return false;
++            }
++
++            for (final AABB aabb : HOPPER_ITEM_SUCK_INDIVIDUAL) {
++                if (aabb.move(shiftX, shiftY, shiftZ).intersects(entity.getBoundingBox())) {
++                    return true;
++                }
++            }
++
++            return false;
++        });
++        // Paper end - optimize hopper item suck in
      }
  
      @Nullable