@Override
    public int getKeyOffset() {
      return this.offset;
    }
A simple form of KeyValue that creates a keyvalue with only the key part of the byte[] Mainly
used in places where we need to compare two cells. Avoids copying of bytes In places like block
index keys, we need to compare the key byte[] with a cell. Hence create a Keyvalue(aka Cell)
that would help in comparing as two cells
hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValue.java