Daily snapshot automatic recovery

[LesnyRumcajs]

Issue summary

It happened and may happen again that Forest is just unable to go past a certain epoch. Be it a lack of state migration (or an incorrect one) or another issue within Forest, the daily snapshot should continue working without manual intervention.

A general idea is as follows - if the snapshot was not generated in X hours, fetch the FilOps snapshot, import it to Forest and then generate our own snapshot. X could be 30, but let's ensure it's easily configurable.

A proper notification should be sent to Slack when that happens.

Other information and links