This came out of investigating the replica_sets failures after setting EMRC=true in EFT. See this patch.

In jstests/replsets/advance_cluster_time.js, we can see several CommandNotSupported errors from the KeysCollectionManager (which I think affects how we gossip the clusterTime). This comes from a check in replCoordImpl and the test works if this code is commented out. Here, we're checking if the storage engine has a SnapshotManager, so that we can decide if we should wait for a target optime to be in the majority committed snapshot.

However, the EFT storage engine does not have a SnapshotManager, so we should consider adding that if it is expected to support snapshots. Otherwise, we'll need to think more about the check in replCoordImpl.