Add a staking genesis sanity check to ensure debonding interval > 0

[ptrus]

The liveness statistics code assumes that the node status for all runtime nodes from the previous epoch exists and can be queried:

oasis-core/go/consensus/tendermint/apps/roothash/liveness.go

Lines 62 to 65 in 52105d9

	status, err := regState.NodeStatus(ctx, nodeID)
	if err != nil {
	return fmt.Errorf("failed to retrieve status for node %s: %w", nodeID, err)
	}

This effetely means that staking deboning interval needs to be >0.

This doesn't affect any real network deployments, as there the staking debonding interval is configured.
Still, it would be nice to have a sanity check to catch this potential misconfiguration.