Radar view for OBSTACLE_DISTANCE message

With the ongoing work to improve obstacle avoidance using the Intel 435i, AP is receiving [OBSTACLE_DISTANCE](https://mavlink.io/en/messages/common.html#OBSTACLE_DISTANCE) messages. It would be great if we could display the output of these messages on the radar view. This would make both development and use of these sensors easier because the user could more easily see what output is coming from the sensor. For example it's helpful in determining if the sensor is aligned forward properly.

Start by locating the radar view and the handling of MAVLink OBSTACLE_DISTANCE messages in Mission Planner. The work is done when the radar view displays the received distance output clearly enough to assess sensor alignment and behavior.

Written by the indexing model from the issue text.