The bulk of the dropDatabase business logic currently sits in a function on the ShardingCatalogClient.
As part of moving the dropDatabase command to the config server, we should move the business logic from the ShardingCatalogClient to the ShardingCatalogManager.

Note, the ShardingCatalogClient hierarchy is:
ShardingCatalogClient base class
--> child class ShardingCatalogClientImpl (the real implementation)
--> child class ShardingCatalogClientMock (has dummy methods)
Moving the dropDatabase function will require deleting code from all three of these classes.
Also note, moving the dropDatabase function will also require updating some unit tests.