Be sensible computing project patch counts

Be sensible computing project patch counts

Django actively fights constructing a query that isn't insane.

So, let's go and just execute a raw one. This is all very standard
SQL so should execute everywhere without a problem.

With the dataset of patchwork.ozlabs.org, looking at the /project/
page for qemu-devel would take 13 queries and 1500ms,
with this patch it's down to 11 queries in ~250ms.
For the dataset of the netdev list, it's down to 440ms from 1500ms.

Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
[stephenfin: Handle projects that have no archived patches and those
 with all patches archived]
Signed-off-by: Stephen Finucane <stephen@that.guru>