The collStats command does not have an IDL defined reply type, so we can use NamespaceStringUtil::serialize to serialize the namespace correctly in the response here and here (the second place special cases appending stats for a timeseries collection).

Let's add tests to native_tenant_data_isolaton_basic_security_token.js that run collStats both on a standard collection and on a timeseries collection (an example of how to create a timeseries collection is here). We can use the "checkNsSerializedCorrectly()" function defined in the test to check the namespaces are serialized correctly.