@InterfaceAudience.Private
public abstract class ScanResultCache
extends Object

Used to separate the row constructing logic.

After we add heartbeat support for scan, RS may return partial result even if allowPartial is false and batch is 0. With this interface, the implementation now looks like:

1. Get results from ScanResponse proto.
2. Pass them to ScanResultCache and get something back.
3. If we actually get something back, then pass it to ScanConsumer.