// ExportToSst exports changes to the keyrange [start.Key, end.Key) over the
// interval (start.Timestamp, end.Timestamp]. Passing exportAllRevisions exports
// every revision of a key for the interval, otherwise only the latest value
// within the interval is exported. Deletions are included if all revisions are
// requested or if the start.Timestamp is non-zero. Returns the bytes of an
// SSTable containing the exported keys, the size of exported data, or an error.