AP_DDS: Add support for NavSatFix publishing from AP

[Ryanf55]

As part of the MVP API for DDS, one commonly used message is NavSatFix.

It is the lat-lon-altitude version of position in WGS-84 coordinate system, which is commonly used to publish GPS data (before fusion).

It can be consumed by visualization tools like Foxglove to show the vehicle on a map.

The publish rate should match the fix rate of the GPS sensor, and the timestamp should match the timestamp from the GPS receiver, not when it's published by DDS. This may require changes in the GPS code to add a callback. Be careful about adding circular dependencies in the code between AP_DDS and AP_GPS.

Tridge: In AP_GPS, look at last_update_time (uint32 ms). If timestamp is different, publish and update. Poll at 1Khz. It may be 5Hz, it may be at 10Hz. Timestamp comparison is cheap.

• Complication: Some GPS produce data, but perhaps yaw may not be update (moving baseline RTK), which may be at a different timestamp. This can be ignored because we don't send yaw in NavSatFix.
• Complication: Last message time vs last update time. Last message time whether for GPS device is still talking, last update time is last complete frame of state. Want the state update from last_fix_time_ms

Test this in SIM_GPS_* to test

1. Losing lock, but still has signal (SIM_GPS_FAIL)
2. GPS cable breaks (SIM_GPS_TYPE to different type)

GPS can set num_instances

Original intent of NavSatFix can be found here: https://wiki.ros.org/sensor_msgs/Reviews/2010-05-31%20GPS%20Proposal_API_Review?highlight=%28PackageReviewCategory%29

[Ryanf55]

I'm hoping some additional fields can be added in time for ROS2 Iron.
See the request here: ros2/common_interfaces#219

If the changes are accepted, this means ArduPilot will have to figure out how to support multiple ROS 2 versions.

[russkel]

I always viewed NavSatFix as rawish sensor data more than an actual position output.
Similar to the way for orientation we use a Pose message with a Quaternion field, and not, say, a MagneticField (https://docs.ros2.org/foxy/api/sensor_msgs/msg/MagneticField.html) message.

As it's appropriate here, I'll mention the option of using the geographic_msgs GeoPoseStamped (https://github.com/ros-geographic-info/geographic_info/blob/ros2/geographic_msgs/msg/GeoPoseStamped.msg) type.

[Ryanf55]

publish GPS data (before fusion)

Yep, as mentioned in the issue publish GPS data (before fusion). It's the raw data from the first GPS. If you want data from AHRS, we can use GeoPoseStamped. Thanks!

[Ryanf55]

Completed by #23533