Add radio settings to ServiceEnvelope

[tiagoad]

The meshtastic.pt MQTT server has all bands (868, 433, 2.4) being sent to the same MQTT topic (for example, msh/2/e/LongFast). Right now, they're trying to enforce a naming scheme that allows to differentiate clients by appending -868 -433 etc to the node name. I am investigating if this is a tooling issue that can be solved (by contributing to the app, map, etc), or an impossibility.

From looking at the protobufs, it doesn't seem to be possible to know which band the message came from through the ServiceEnvelope packet in MQTT, unless stated in the topic, but please correct me if I'm wrong.

My proposal would be to add a field to ServiceEnvelope with the band the receiver is operating in.