Following SERVER-67155, we will need to modify calls to existing NamespaceString serializers/deserializers to now call the new NamespaceString utils class.  This involves modifying call sites directly calling the serializers/deserializers, marked by TODOs modified in SERVER-67155, as well as removing any old functions from NamespaceString as we swap them out.  Then we should swap out the serialize and deserialize functions that are set for the IDL "namespace_string" type. 

We will likely need to make this utils library available for other libraries to link in as well used with the IDL parser, then write or modify some consumer-side tests to validate that consumers are behaving correctly according to the output of the serializers/deserializers when used with various combinations of the featureFlagRequireTenantId/multiTenancySupport flags.