Item packer gives off unexpected comparator values

[Daniel99j2]

Not sure if this is intended, but the comparator values are not as they should be:

1. When only a few items are in it, it does not give off a signal (in vanilla it would)
2. Shulkers do not give off the same values as if they had been placed in the world. The 1st issue can be fixed by just a Math.max() statement. The 2nd issue probably can be fixed by making the function return ScreenHandler.calculateComparatorOutput (what shulker boxes use) if it is not a bundle.

This should hopefully make the item packer's comparator match the base game and more intuitive.