Fix mavlink unresponsiveness / lateness.

[joaoantoniocardoso]

Finally, the clogging is solved.

lesson learned: Do not sleep on network-receiving, or channel-receiving loops.

The CPU usage on RPI4 spikes +6% when exchanging information back and forth with the GCS.

• [x] Tested locally
• [x] Tested with the ROV (RPI 4)

Closes #354