[Flight] JDBC driver: make connect timeout adjustible

[lidavidm]

Describe the enhancement requested

• The default connect timeout is 30 seconds. This is rather painful when the server returns an address that isn't reachable. (Example: the server is deployed on a Kubernetes cluster that is being accessed via proxy/port-forwarding, and the server has a separated data plane/control plane.)

[lidavidm]

Partly split out to #661.