feat: use hasql-pool-0.10, add db-pool-max-idletime (#2786)

- new option db-pool-max-idletime limits the maximal idle time of a
  postgresql connection, defaults to 30 seconds
- this essentially restores the db-pool-timeout option from versions
  <=10, with more specific name

test/io/configs/expected/defaults.config

@@ -7,6 +7,7 @@ db-plan-enabled = false
 db-pool = 10
 db-pool-acquisition-timeout = 10
 db-pool-max-lifetime = 1800
+db-pool-max-idletime = 30
 db-pre-request = ""
 db-prepared-statements = true
 db-root-spec = ""