When change streams are in a `getMore` loop against an open cursor, they do not respect the read preference defined in the connection if there is a promotion event that invalidates the primary / secondary status of the server it is streaming from. This feature is to leverage SDAM and monitor the server's status, and if the read preference is invalidated, close the cursor noting the resume token, re-open against a read preference compatible node, and resume streaming from the resume token. This feature is key in order to keep load off the primary node.