Update change_stream_null_existence_eq_rewrite_test.js for newly-added events

The change_stream_null_existence_eq_rewrite_test.js test performs equality and existence checks against every fieldpath it observes in a change stream. We should update this test to include the newly-added events. This should only require adding some new operations to the performWriteWorkload function, and ensuring that the stream runs with showExpandedEvents:true.