A normalizer which merges very small size regions with adjacent regions.(MergeToNormalize)

There are scenarios where we have seen around 5% of total regions with a size of 0 bytes and another 5-6 % regions with size in a few bytes. These kinds of regions increase with time considering we have TTL over the rows. 

After exploring the option of RegionNormalizer and doing some quick runs we found that that is not suitable considering it also splits the regions and merges to normalize. What we really want is to split as per Split policy and merge very small regions with adjacent regions to make sure we reduce 0-byte regions.

We can plugin this normalizer using the property "hbase.master.normalizer.class"