This commit introduces large_partition_handler class, which can be used
to take additional action when large partitions are written.
It comes with two implementations:
* NOP, used in tests, which does nothing on large partition
update/delete
* CQL TABLE, which inserts/deletes information on particular sstable
to system.large_partitions table, in order to be retrievable from
cqlsh later.
References #3292
