Fetch all series for patch/cover viewing

Fetch all series for patch/cover viewing

e.g. a 10 comment patch goes from 26 queries in 17-20ms down to 20
queries in 12ms.

A 67 comment cover letter goes from 14 queries in 16ms down to 8 queries
in 8ms.

So, effectively, a near 2x perf improvement.

Previously, at several points we were asking for the latest series and
then asking for all the series. Since there just usually aren't *that*
many series, fetch them all and take the first one if we need to.

Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
[stephenfin: Fix typos in the template and ensure patches from all
 series are shown]
Signed-off-by: Stephen Finucane <stephen@that.guru>