[wpinet] Add mDNS discovery tests and fix mDNS JNI bugs

[mcm001]

In #8681 we discovered that multicast service types need to be valid (end with _tcp or _udp), or else errors are silently swallowed. Let's make our C++ unit test use a valid name and also check that it works. I think if we should/shouldn't do this is up for debate still.

I also discovered two bugs in the JNI code that lead to incorrect results being returned

• Return array index was always 0
• Use of JLocal for the return value seems to mean that the array will always be NULL in java

[mcm001]

We can also retarget this at main if you'd prefer

[Gold856]

Lot of printfs. Should those be printlns?

[mcm001]

It looks like none of our runners include avahi-daemon, leading to these test failures? https://github.com/actions/runner-images/blob/main/images/ubuntu/Ubuntu2404-Readme.md

Would we prefer

• Deleting these new tests
• Installing avahi
• secret option 3?

[mcm001]

I need some help understanding what to do about the tsan warnings in https://github.com/wpilibsuite/allwpilib/actions/runs/23174224436/job/67332769813?pr=8682 -- are these real/something we need to address?

windows ci failed because of a flake in DifferentialDrivetrainSimTest.Convergence, then another flake in TimedRobotTest.TestMode

[mcm001]

Blocked on wpilibsuite/docker-images#71