provide a db storage for alert intermediate states

[FrankChen021]

IAlertStateStorage has two implementations now, one is local memory, the other is redis.
For the first one, the state information loss if the application restarts.
For the 2nd one, users have to deploy a redis instance/cluster

To overcome these two problems, a db-based state storage can be provided for trade-off.
to reduce interactions between db and the alerting application, before evalutation, loading all states from the db, and after evaluation, flush all new states back to the db.