Support shard/collection deletion in shared storage

The Solr Cloud deletion APIs for collections and shards are not currently supported by shared storage but are an essential functionality required by the shared storage design. Deletion of objects from shared storage currently only happens in the indexing path (on pushes) and after the index file listings between the local solr process and external store have been resolved.

This task is to track supporting the delete shard/collection API commands and its scope does not include cleaning up so called “orphaned” index files from blob (i.e. files that are no longer referenced by any core.metadata file on the external store). This will be designed/covered in another subtask.