Add refresh_status migration
Record ems refresh failed or succeeded
Refactoring refreshers' core logic into mixin

The main purpose here is to introduce a common way to set the refresh status and
handle some common logging for the EMS Refresh process.

Two caveats:

1. The status/logging was copied/pasted for VC Refresher since the logic there
   is quite a bit different from the other refreshers.
2. The NonEmsRefresher wasn't touched, since it's not an EMS refresher