Add camera offset and use it for CAM log message

for Copter 3.5 and RTK, it will be very useful to generate real position of camera by adding offset x y z parameter for CAM beetween gps antenna centroid and camera sensor.

Like this position of camera will be correct when multirotor lean angle.

Start by tracing Copter's CAM log message generation and the handling of the GPS antenna centroid and camera position. Determine how an x/y/z offset should be applied for Copter 3.5 and RTK, then verify that CAM messages report the camera's real position while the multirotor is leaning.

Written by the indexing model from the issue text.