[1.16] MultiInventoryComponent does not rebuild the `null`/internal side

[SquidDev]

Forge's capabilities support fetching a capability instance for the "null" side. In the case of inventories, this is generally defined to return the "whole" inventory of a tile (rather than a subset of slots like other sides do).

However, Titanium's MultiInventoryComponent implementation always returns an empty LazyOptional. From my reading of the code, this is because the add method only rebuilds the lookup for the cardinal directions, and not the null side:

Titanium/src/main/java/com/hrznstudio/titanium/component/inventory/MultiInventoryComponent.java

Lines 44 to 49 in 279f681

	public void add(Object... component) {
	Arrays.stream(component).filter(this::accepts).forEach(inventoryComponent -> {
	this.inventoryHandlers.add((InventoryComponent<T>) inventoryComponent);
	rebuildCapability(FacingUtil.Sideness.values());
	});
	}

This means that mods which use getCapability(ITEM_HANDLER_CAPABILITY) (rather than getCapability(ITEM_HANDLER_CAPABILITY, side) will not be able to insert into Titanium's inventories.