Default CAN binding message support does not match agl-vcar definition

When the agl-service-can-low-level CAN binding was updated prior to Icefish release, the generated message support file that was checked in was apparently generated from some version older than the agl-vcar signals.json file that was in the repo, which contained message/signal definitions for the steering wheel support demo-ed at CES 2020.  An updated version of the generated source file needs to be added so that the configuration matches what was present by default in Halibut, and make the in-tree signal-composer configuration functional again.