DRIVERS-1975:
sync new unified spec test changes from this commit 9652564 .
a new option to the change stream pipeline stage has been added (`showExpandedEvents`)
new change stream events were added
Note: Followup test fixes have been merged. Make sure to sync with 8da1a8990 and 51741620 ( DRIVERS-2417 ) as well.
Not Needed
Description
This ticket was split from DRIVERS-1975, please see that ticket for a detailed description.