Convert 'last-rendered' to sqlc. The query is slightly suboptimal.
There's a bug in sqlc: the `ON CONFLICT DO UPDATE` clause is generated
incorrectly. See https://github.com/sqlc-dev/sqlc/issues/3334 for more
info.
Tweak the logging a little bit so it's less noisy, properly warns when the
Shaman checkout dir cannot be removed, and optimise the database query
a bit (by just fetching the one field that's needed, instead of the entire
job).
Deletion still works the same.
This is a bit more work than other queries, as it also breaks apart the
fetching of the job and the worker into separate ones. In other words,
internally the persistence layer API changes.
This makes it easier to later also create `query_workesr.sql`,
`query_meta.sql` etc. so that the sqlc-generated code can follow the
same subdivision as the persistence service code itself.
No functional changes.
