Remap orbit stick input when vehicle faces tangential

[MaEtUgR]

Describe problem solved by this pull request
When flying an orbit with the yaw behavior ORBIT_YAW_BEHAVIOUR_HOLD_FRONT_TANGENT_TO_CIRCLE where the vehicle is facing tangential to the circle and hence facing the direction of travel it's unintuitive to change the radius and velocity of the orbit with the usual stick mapping. This is because usually the stick input is mapped in the body yaw frame.

Describe your solution
I changed the stick input to also act 90° offset compared to when flying with the vehicle facing the center of the circle. Such that's intuitively in body yaw frame.

Doing that I found the direction of where the vehicle is facing and hence also how the stick input is mapped would change 180° when switching rotation direction. This makes direction switches by stick unusable. To work around the problem I made the vehicle go backward when the rotation direction is switched by stick input.

Test data / coverage
This was tested in SITL and on a real vehicle that mostly uses ORBIT_YAW_BEHAVIOUR_HOLD_FRONT_TANGENT_TO_CIRCLE.

[sfuhrer]

For me this way of controlling velocity feels natural, including the direction switch (frontwards<-->backwards).