Summary

Extend the Unified Test Format and driver test-runner to optionally support exhaust cursors.

Motivation

It may be occasionally necessary to test connection state while streaming moreToCome batches for a cursor where the exhaustAllowed bit flag is set on OP_MSG. For example, DRIVERS-2884 requires testing that drivers that support exhaust cursors do not attempt to discard pending responses during a socket timeout.

This is low priority as only two drivers support this behavior: libmongoc and PyMongo.

Acceptance Criteria

Add exhaust to the cursorType enum on all cursor-returning operations (e.g. createFindCursor, runCursorCommand).