CreateAndConnect connects and creates the requested DB (dropping if exists) then returns a new connection to the created DB.

ExecPgbench returns a ready-to-run pgbench Cmd, that will run against the db specified by `pgURL`.

RunOne executes one iteration of the query batch that `pgbench` executes.

SetupBenchDB sets up a db with the schema and initial data used by `pgbench`.

SetupExec creates and fills a DB and prepares a `pgbench` command to be run against it.