protected List<RegionInfo> uniformRegions(int numRegions) {
    List<RegionInfo> regions = new ArrayList<>(numRegions);
    byte[] start = new byte[16];
    Bytes.random(start);
    byte[] end = new byte[16];
    Bytes.random(end);
    for (int i = 0; i < numRegions; i++) {
      Bytes.putInt(start, 0, numRegions << 1);
      Bytes.putInt(end, 0, (numRegions << 1) + 1);
      TableName tableName = TableName.valueOf("table" + i);
      RegionInfo hri = RegionInfoBuilder.newBuilder(tableName).setStartKey(start).setEndKey(end)
        .setSplit(false).build();
      regions.add(hri);
    }
    return regions;
  }
This assumes the RegionPlan HSI instances are the same ones in the map, so actually no need to
even pass in the map, but I think it's clearer.
@return a list of all added {@link ServerAndLoad} values.
hbase-balancer/src/test/java/org/apache/hadoop/hbase/master/balancer/BalancerTestBase.java