[WIP] Added support for resetting wind states to external observation

[RomanBapst]

Solved Problem

Initial work to support https://github.com/mavlink/mavlink/pull/2122

Once the mavlink message is available I need to fetch the data from the command and push it into the estimator.

Changelog Entry

For release notes:

Feature: Added support for MAV_CMD_EXTERNAL_WIND_ESTIMATE