SHARED replicas can recover on clean disk

One of the benefits of SHARED replica is that it provides the ability to run SolrCloud with ephemeral disk(containers). Since the source of truth is in shared store, we can safely recover index from there. But currently there is no support to reason about the core descriptors that do not live locally on the disk. The purpose of this task is to discover missing core descriptors for SHARED replicas from ZK.