SERVER-47970 added support to retrieve atClusterTime from snapshot read cursor responses (find, getMore, aggregate).

We are also planning to support "distinct" for snapshot. However, "distinct" doesn't return a cursor but a list of results. So we need a different way to retrieve the atClusterTime from the "distinct" results (maybe there will be a DistinctResult object that has the values and atClusterTime). We will wait to see what the Drivers API for "distinct" is after DRIVERS-815 and bring the shell into compliance.

And we want to also bring cursor responses in the shell (find, getMore and aggregate) into compilance too after we have a driver spec.