Implement fan control and rpm monitoring

You can call ob1SetFanSpeeds() and given it a percentage speed. From scanwork, you can call get_fan_rpms(0) and get_fan_rpms(1) to get the most recent sampling of the fan RPM (updated twice per second). NOTE: This contains some changes that re-enable firmware uploads too - more to follow Would normally put those in a different branch/MR, but it's a bit of work to untangle them now