Adds a flag to skip thread head migration that can be used when we know migration is not needed, as in, it's already been run. This should greatly reduce the time to deploy.
I started updating libp2p to 0.15.1, which requires an update to go-datastore. Those changes require we wire context into all the datastore apis we use (keystore, logstore, db). I pushed that wip work to https://github.com/textileio/go-threads/tree/sander/libp2p-0.15.1. I think going down that path means a major version bump because the external DB apis would need to take context. Paused for now.