This commit adds a system.large_partitions table, which can be used
to trace largest partitions of a cluster.
Schema: (
keyspace_name text,
table_name text,
sstable_name text,
partition_size bigint,
key text,
compaction_time timestamp,
PRIMARY KEY((keyspace_name, table_name), sstable_name, partition_size, key)
) WITH CLUSTERING ORDER BY (partition_size DESC);
References #3292