Ordered Quantities: Faster For High-Volume Products

Ordered-quantity calculations return much faster for products with a lot of order history. The query for a hot SKU used to take around 20 seconds and get worse under load; it now takes about 7 seconds with the same results. The V2 unassigned-quantity calculation also stopped joining every warehouse just to zero most of them out — totals are unchanged, it's just less work per call.