Interactive Stack selector shows downed deployments

[jordanstephens]

We may want to preserve the ability to redeploy a previously downed stack, but we also don't want to show very many old stacks that we have no plan to ever use again. I think there are a few potential improvements we could make along these lines:

1. differentiate "downed" stacks from actively "up" stacks, so that the user can identify them as "downed"
2. consider only showing up-to a fixed number of downed stacks, sorted by most-recent activity in descending order, to avoid an infinitely growing list.
3. we may want to implement support for permanently deleting records of downed stacks