Support MAVLink Signing

[ES-Alexander]

The MAVLink protocol has support for message signing / authentication, which BlueOS should facilitate using.

Ideally this should be integrated with (or at least facilitated by) its own authentication (per #3484).

[joaoantoniocardoso]

I see that for MAVLink via radio, yes, that can help.

But for most of our use cases, I'm not sure whether this is a significant security improvement. For ROV and Boats, we are using other protocols around MAVLink that can be better secured, like SSL for TCP/UDP/HTTP/WebSocket.

When we decide to implement it, good to remember that at least the following backend tools need to be changed to support it: mavlink2rest, mavlink-server (and rust-mavlink-codec), and mavlink-camera-manager.