Major Description
I added the RegionScanner.nextRaw(...) to allow "smart" client to avoid some of the default work that HBase is doing, such as
{start|stop}RegionOperation and synchronized(scanner) for each row.
Metrics should follow the same approach. Collecting them per row is expensive and a caller should have the option to collect those later or to avoid collecting them completely.
We can also save some cycles in RSRcpServices.scan(...) if we updated the metric only once/batch instead of each row.