java/driver/jni: implement executePartitioned

[lidavidm]

What feature or improvement would you like to see?

We'll also need to test against Flight SQL.

[metegenez]

Happy to take this, but how do we test multi-partition fan out against FlightSQL? None of the FlightSQL servers in CI support multi partitions. I can test locally but we should cover this in CI too, right? If you have a suggestion on how to test it properly, the implementation itself is straightforward.

[lidavidm]

Sorry, this is already taken

[lidavidm]

#4263