Enhancement: Control of auxiliary servos (PixHawk)

The use of the auxiliary servos would be a huge benefit on the road to going RCless. Can the list of servos in the main flight data tab be increased as well as for waypoint control in the planner?

Start by locating the UI code for the main flight data tab and the planner's waypoint-control servo list. Trace how the existing auxiliary servos are enumerated and identify the limits in both views. Done means both interfaces expose the increased servo list for PixHawk control, with their existing workflows still functioning.

Written by the indexing model from the issue text.