Overloading existing methods in CosmosStore and BlobStore class for system resources

Problem:

The cosmosStore class today is the facade to perform CRUD on data partition related cosmos dbs. All the methods in this class are tightly coupled with data-partition-id. Since the system data resources won't be coupled with a data-partition-id, the existing facade can't support CRUD on system resources. Same problem exists with BlobStore class

Changes in MR:

1. Enhanced the current CosmosClientFactory to return system level cosmos clients too.
2. Enhanced the current BlobServiceClientFactory to return system level cosmos clients too.
3. Overloaded existing methods. The new methods don't accept data-partition-id parameter
4. Minor code refactoring
5. Added UTs