Enhancement: New Flight Logic Command DO_Turn

#### Enhancement details
A desired feature would be a Logic command like DO_Turn_Left and DO_Turn_Right. The inability to determine and command a turn direction is an issue for Beyond Visual Line of Sight Flight Operations within a defined Geo Fence operations area. The unpredictability of turn direction is undesirable and can potentially result in the loss of aircraft in certain situations.

#### Version
Current version in use is 1.3.63

#### Platform
[ ] All
[ ] AntennaTracker
[ ] Copter
[x] Plane
[ ] Rover
[ ] Sub

#### Airframe type
Fixed wing

#### Hardware type
Pixhawk

#### Logs
none

No files or tests are named. Start by tracing how Mission Planner handles Plane flight-logic commands, then clarify the required left- and right-turn behavior with maintainers for fixed-wing operations. Done means the command semantics, affected entry points, and acceptance checks are agreed and implemented.

Written by the indexing model from the issue text.