feat: add db-pool-timeout alias

For db-pool-max-idletime

test/io/configs/aliases.config

@@ -1,4 +1,5 @@
 db-schema = "provided_through_alias"
+db-pool-timeout = 5
 max-rows = 1000
 pre-request = "check_alias"
 role-claim-key = ".aliased"

test/io/configs/expected/aliases.config

@@ -7,7 +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-pool-max-idletime = 5
 db-pre-request = "check_alias"
 db-prepared-statements = true
 db-root-spec = "open_alias"