moving platform: add IMU sensor

[mbjd]

Follow-up to #83.

As discussed in PX4/PX4-Autopilot#24471 we will keep the platform simple and refrain from interfacing with PX4 for now. Instead we add this IMU sensor as a very simple way to get the pose info from the simulation.

[Jaeyoung-Lim]

Why do you need an imu sensor? You can already get the pose of the platform from simulation

[mbjd]

True, we could copy the logic from GZBridge poseInfoCallback, this is technically not needed.

I thought an explicitly added sensor would make it more obvious that this information is used, and better reflect the real situation which involves the platform measuring and communicating its position, velocity, and orientation. Also, it makes it easy to later add noise in a standard way rather than adding it manually to the simulation pose in the receiver.

If you're strongly against it still, I'm open to doing it the GZBridge way.

[Jaeyoung-Lim]

@mbjd Unless you plan to explicitly simulate a sensor onboard the moving platform, I dont think there is a good reason to simulate it.

What information of the moving platform being used by the drone?

[mbjd]

Global position, velocity, and orientation. Sent with this message: mavlink/mavlink#2238 or similar, subject to change :)