This PR adds a new step in the reloadValidators cron. It gets (with a single call to beaconapi client) the index and statuses of all pubkeys currently stored in db.

• gracefully handlers errors by not writing in db and only logging. Rest of the cron is unchanged.
• logs through console when it fetches indices/statuses for the first time or these change from the last time fetched
• added unit test with mock beaconchain responses.