HBASE-24583 Normalizer can't actually merge empty regions...

when neighbor is larger than average size

* add `testMergeEmptyRegions` to explicitly cover different
  interleaving of 0-sized regions.
* fix bug where merging a 0-size region is skipped due to large
  neighbor.
* remove unused `splitPoint` from `SplitNormalizationPlan`.
* generate `toString`, `hashCode`, and `equals` methods from Apache
  Commons Lang3 template on `SplitNormalizationPlan` and
  `MergeNormalizationPlan`.
* simplify test to use equality matching over `*NormalizationPlan`
  instances as plain pojos.
* test make use of this handy `TableNameTestRule`.
* fix line-length issues in `TestSimpleRegionNormalizer`

Signed-off-by: Wellington Chevreuil <wchevreuil@apache.org>
Signed-off-by: Viraj Jasani <vjasani@apache.org>
Signed-off-by: huaxiangsun <huaxiangsun@apache.org>
Signed-off-by: Aman Poonia <aman.poonia.29@gmail.com>
5 files changed