Improve mining waypoint

- Refactored SlotTextAdders to take in ItemStack and int slotId rather than Slot
- Refactored the renderSlotText method from HandledScreenMixin into SlotTextManager and added an overloading function that takes in the itemstack, slot id, x and y and the previous function with the Slot parameter just delegates to it with the relevant fields from that Slot object
- As a result of the above 2 changes the logic in CommunityShopAdder had to be changed too, now it figures out the screen from the method calls to `getText` rather than the Slot's inventory.
- Fixed slot text not being rendered in backpack preview
- Added private constructor for BackpackPreview (because it's all static methods anyway)

fix issues. and remove unnecessary square root

As seen in the new titanium equipment for mining

Should be less conflicting with other things