Handle driver misuse gracefully

[mhidalgo-bdai]

Feature description

The SpotROS ROS 2 driver node operates on the premise of proper use e.g. to release an eStop, an eStop must have been acquired. Failure to do so is met with cryptic exception messages. It would be beneficial for users if these cases were handled gracefully instead, with descriptive error messages.

Implementation considerations

Propagating SDK errors consistently and limiting ROS 2 service and action interfaces' operation to the robot states in which they are applicable (e.g. don't try to release an eStop if none has been acquired, don't try to move if the robot is powered down) would go a long way.