[test/querier] use the new connection api (part 1/3) In devtools/repotest, we provide a simple `.qexecute` with autocommit, and we use it (where possible) in unittest_querier. Note that the .session object is a real session, not the magic property found in CubicWebTC test classes.

option_group_changed('cleanup-session-time', 'web', 'main')