Append New Repos To New Run Group

[dyoder]

We currently write the “memoized” run groups at the end of a run command. This allows us to save the optimal run order for the repos for which the run command succeeded. On subsequent runs, we prepend the unsuccessful repos (or any new repos) to the first run group. We should probably append these instead to a new run group at the end.

The rationale for appending is that we can recreate the success of the previous run right out of the gate before attempting the failed (or new) repos..