Define specific rover commands and their protobuf equivalents

[Levi-Lesches]

Perhaps this should be under the new Rover API repo instead, but filing here for now.

We need to convert all the possible commands from https://github.com/BinghamtonRover/BurtOS-2/blob/main/src/subsystem/can/constants.hpp to both Dart representations and their Protobuf equivalents.

I don't have much experience with Protobuf yet, but I can see that all these commands will have arguments, so the Dart representation would need to be something like

class RoverMessage {
  final int id;
  final double value;  // or int?
}

and then later, in the networking service, we would have a function

Future<void> send(RoverMessage message) { }

Then of course, we'd need to make the protobuf message files as well.

[Levi-Lesches]

Being tracked by BinghamtonRover/Protobuf#1 with a different implementation