Support ArduPilot "Partner Support Proxy"

https://ardupilot.org/dev/docs/support_proxy.html

It's already supported in mavproxy + MissionPlanner + QGroundControl, so if we want to be a first party GCS then we should provide similar access to the support network if it's possible to do so :-)

Start with the ArduPilot support_proxy documentation linked in the issue and compare the existing MAVProxy, MissionPlanner, and QGroundControl implementations it names. Define the required integration and verify that Cockpit can provide equivalent first-party support-network access.

Written by the indexing model from the issue text.