Detect buffer over and under-runs

[ghost]

Although we have the ability to track the "cycle" of the ring buffers, we have never integrated the ability to detect when buffer under or overruns occur. For example, if we don't call buffer.read() fast enough, it's possible for the RPvdsEx circuit to overwrite unread data in the buffer before it is transferred to the computer. While these are generally rare occurrences, they do occur especially on older workstations.

[larsoner]

Merged with master to get CIs to run, though they don't test much. I don't have hardware to test this but the code looks reasonable, feel free to self-merge if you're happy @buranconsult

[ghost]

@larsoner All tests pass on a machine with the RZ6.

[larsoner]

Thanks @buranconsult !