Check if the block keys, index keys can be used as Cells instead of byte[]

While doing HBASE-10531 we can observe that most of the comparison happens between the key part of the KVs. If suppose we need to make use of Cells and get rid of Kv.getBuffer() then the Keys with which the comparison are done like the block keys, index keys etc should also be changed to Cells and internally do the comparison as cell. This issue would help to brain storm this and implement the feasible soln.