dashboard errata widget performs large/slow sort in sql
On a system with lots of errata and hosts, the errata dashboard widget can take upwards of 90 seconds to load. This depends on the size of `katello_content_facet_errata`, and the size of the largest errata's description/summary/solution text.
If the join between the errata and the content facets is larger than work_mem, the sort will need to be done on-disk, resulting in extremely slow dashboard load time. work_mem should not be increased if possible, as it is used for each query and subquery.
Fixes #16763: do not sort over entire `katello_errata.*`
The dashboard's errata widget had a query that sorted over
`katello_errata.*`. Instead, use `DISTINCT ON` to sort only on `id`
This is similar to 4667141bf. That patch was backed out in favor of
42502063, this patch re-adds the same optmization but in a smaller