Add relposheading in process fix uavcan driver (AP Periph Dronecan Dual RTK support)

[dirksavage88]

Solved Problem

Adds support for dual RTK heading via AP Periph, which publishes heading as a distinct message (RelPosHeading) instead of via the ecef position fields.

Fixes #22520

Solution

• Add sub callback for relposheading within GNSS sensor uavcan driver
• Process heading information and validity in process fixx method

Changelog Entry

For release notes:

Feature: Add support for AP Periph (dronecan) dual GPS heading setups
New parameter: None
Documentation: Pending doc update PR in PX4 user guide

Alternatives

Create a sub to the sensor gnss relative uORB topic directly in EKF2

Test coverage

• Tested using dual Holybro ZED-F9P dronecan nodes and pixhawk 6xrt

Context

TODO: post log
Pending doc update PR: PX4/PX4-user_guide#3406

[dirksavage88]

@vincentpoont2

[vincentpoont2]

@dirksavage88 Anything we can assist on our end?

[dirksavage88]

@vincentpoont2 I am having issues getting the rover RTK F9P to get Fix type of fixed (6). It only reports fix type of 3 or 4 even after sitting for a while. (Similar issue to this post: https://discuss.ardupilot.org/t/heading-informations-via-moving-baseline-configuration-gnss-antenna-setup/113674/8)

Other than this issue, I have some questions for the maintainers on how to integrate the gps yaw offset correctly, since it is handled differently in PX4 than what ardupilot is doing.