Externalize database components separately

Customer's issue: When externalizing the database components, all three DB components (system-redis, backend-redis, system-database) have to be externalized at the same time.  This brings huge migration challenges for customer. There is no way if they need to only migrate single component alone.

Expectation: To have more flexibility, the operator can support the customer by letting customer to decide which database component they want to externalize. 

In this case, customer only want to externalize backend-redis, leaving the others inside OCP cluster.