ReplicationConsistencyMarkersImpl::refreshOplogTruncateAfterPointIfPrimary parses the Optime from an oplog entry twice. The code should be change parse it only once. Also, we should take advantage of IDL's ability to disable duplicate field checks.

I have not measured the perf benefits of this change separately.

POC: https://github.com/10gen/mongo/commit/096fabc8c3bc619bfa8b884fc2063f3a8d7cf884#diff-8d3dbd3c29a007065eacb3af7184c7225585b5f0d5d873eeeb981152f207daf0