Reimagine ceph-csi charm with the reconciler pattern

[addyess]

Addresses LP#2068524

Overview

The patterns employed in this charm were difficult to reason about, and in some cases changes occur with no notifications to the charm via config changes or relation changes. Because of this, it's better to employ this charm with a reconciler pattern which can check the necessary state of the charm before configuring/changing the cluster

Details

• Adds the charm-lib-reconciler library
• Convert the merge_config method to act as the reconciler function
• Careful to not use any 1.30 branch reconciler feature so this could be backported to the 1.29 branch if necessary
• Greatly reduce unit testing
• Integration testing only changed to support a different "active" status message

[HomayoonAlimohammadi]

Great work, thanks a lot @addyess! LGTM.