[Java][Flight] Add caching of FlightClients to JDBC

[jduo]

Describe the enhancement requested

When getFlightInfo reports a list of endpoints, the driver internally creates a FlightClient for each endpoint that reports a Location. These clients can benefit from being cached/pooled since a server will likely re-use endpoints for subsequent queries. This should likely be a configuration option.

The driver should also check if the Location at an endpoint is the same as the original location used when calling getFlightInfo and avoid creating a new FlightClient in this case.

Investigate using https://github.com/ben-manes/caffeine for caching.

Component(s)

FlightRPC, Java

[lidavidm]

I'm going to take a look at this. Another issue that's cropped up is that if the server returns an endpoint that isn't addressible (e.g. the data servers are in the cloud and the client is talking to the control plane via proxy), then the client hits the full 30 second Netty connect timeout on every attempt.

[lidavidm]

If we could cache failed attempts and avoid them on subsequent attempts that would help with this (along with caching existing clients and configuring the timeout).