Implement copy-on-write on the CollectionCatalog. Where its data structures that contain shared pointers are copied.

The new catalog instance should be able to be installed with atomic compare-and-swap and we can remove the catalog mutex that is currently there.

Lock-Free read operations hold a shared_ptr to a CollectionCatalog consistent with the established storage snapshot and may perform multiple lookups from this instance that all is consistent with the storage snapshot.

This should allow us to support DBDirectClient in Lock-Free Reads.