Currently, we use NamespaceStringUtil::deserialize to parse NamespaceStrings read both from command requests and from on-disk state. These should actually follow separate rules, so we should create separate functions. For now, we can leave the behavior as the same (to be changed in SERVER-70740), but this ticket should focus on creating the separate functions, and ensuring we change out existing calls to deserialize to call the correct function. Note that we can only specify one deserialize function for the namespace_string type defined in basic_types.idl, so we may need to have some sort of function that takes in info about whether we're parsing a command type or not.