feat: log exit code of every command that is run — radicle-ci-broker

Signed-off-by: Lars Wirzenius liw@liw.fi

             .map_err(|err| MessageHelperError::Command("bash", err))?;
         let exit = output.status.code().unwrap_or(NO_EXIT);
         adminlog.writeln(&format!("runcmd: exit={exit}"))?;
         if exit != 0 {
             adminlog.writeln(&format!("runcmd: exit={exit}"))?;
             indented(adminlog, "stdout", &output.stdout);
             indented(adminlog, "stderr", &output.stderr);
         }