Airflow/Wind sensor

[henrykotze]

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🎉 New feature

Summary

This adds an airflow sensor. These sensors are generally used to measure wind and are ultrasonic devices, measuring the airflow speed and direction using the Doppler effect.

Here is some use cases of such sensors from a manufacturer sensor which we have used.
https://fttechnologies.com/case-studies.

This is part of a larger plan to support an airflow sensor in PX4. @dagar

Test it

Test are added to ensure correct use.

Some things to consider

There exist airflow/wind sensors which provides a 3D vector of the airflow its measuring. So I can see a later addition of adding more properties to the messages, however I have only experience with the 2D sensor, and these properties are the most relevant to them