[dev] Protobuf (FPM) usage survey

Hello FRR users and developers, since some extensions to the FPM interface are currently happening, it'd be nice to know how much the Protobuf interface is used. We know the netlink encoding is well used, but we don't have data for Protobuf. If you're using **Protobuf** FPM, please send a mail (in private if necessary.) Again just to be clear: this is about Protobuf FPM, NOT Netlink FPM. Cheers, -David