psql: Add test for query canceling
Query canceling in psql was accidentally broken by
3a5130672296ed4e682403a77a9a3ad3d21cef75 (since reverted), so having
some test coverage for that seems useful.
Reviewed-by: Fabien COELHO <coelho@cri.ensmp.fr>
Discussion: https://www.postgresql.org/message-id/
18c78a01-4a34-9dd4-f78b-
6860f1420c8e@enterprisedb.com