AP_DDS: ArduPilot Parameter Reading/Writing through DDS interface

[PQuill33]

It would be helpful to have read/write access to ardupilot parameters for all vehicle types through the ROS2/DDS interface.

Proposed Solution
Use ros2 service calls to set/read parameters from ArduPilot by exposing the SetParameters and GetParameters interface from rcl_interfaces.

To set a parameter:

• Create /ap/set_parameters service of type rcl_interfaces/srv/SetParameters.srv
• Response is an array of type rcl_interfaces/msg/SetParametersResult.msg

To retrieve a parameter:

• Create /ap/get_parameters service of type rcl_interfaces/srv/GetParameters.srv
• Response is an array of type rcl_interfaces/msg/ParameterValue.msg

I would add code to the AP_DDS_Client interface to get/set the parameters based on the service call.

Alternative Approach
Is it possible to declare the ardupilot parameters in a way that the ros2 param set/get CLI works? My concern is that there are a lot of parameters and I'm not sure the best way to declare them all for this kind of usage.

Platform
[ X ] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[ ] Rover
[ ] Submarine

Additional context
rcl_interfaces: https://github.com/ros2/rcl_interfaces

Similar to issue in ticket: #23309

[PQuill33]

Here is a draft PR with some work towards a set parameter service
#28298