The change streams sharded cluster suites will run tests in jstests/core with a new change_streams hook in Python that does the following

• Open a change stream every X tests where X is random from 0 to 10 to cover potential edge cases.
• run the background stepdown hook with downgrade
• wait for X tests to run
• Wait for change streams to complete and ensure there are no crashes and go back to step 1

Commands that invalidate change streams (i.e. ones that are not compatible with change streams) will need to be excluded in the suite YAML.

We'll file a followup ticket for Query to implement targeted tests for downgrade of change stream invalidate events. We should also check if there is existing test coverage