[Feature Request]: Store Via MQTT in the NodeDB

[garthvh]

Platform

NRF52, ESP32

Description

The amazing new via mqtt field on mesh packet works really well while you are connected to the network, but essentially gets reset when you connect to a device as this field is not in the nodeinfos that come over wantconfig.

[thebentern]

Perhaps a protobuf to indicate whether the packet was received via any other means than lora? This would future-proof against other high-bandwidth delivery messages on the mesh like BLE, once we get around to that one as well.

[andrekir]

done in #3315