CLI mode should have watch for a sigterm, sigkill, sighub, etc signal that logs when the program exits

[kminehart]

Whenever a build finishes successfully or errors, we submit a new log:

When we find an error: https://github.com/grafana/shipwright/blob/main/shipwright.go#L148

When it finishes successfully: https://github.com/grafana/shipwright/blob/main/shipwright.go#L155

But if someone sends a sigterm (ctrl+c), the "execution completed" log never occurs. We should watch for os.Signals in the Done() function, and log an "execution completed" with a "terminated" status: https://pkg.go.dev/os/signal