cbcollect - Log partition level stats during cbcollect

As a part of cbcollect, please log the partition level stats in couchbase.log for each index on a indexer node. The partition level stats can be retrieved using the following curl call:

http://localhost:9102/api/v1/stats/<bucket_name>/<index_name>?partition=true

Background:

Partition level stats are aggregated and logged as a part of periodic stats (every one minute) in indexer.log. Logging them with out aggregation would flood the logs and we can lose valuable information at the time of debug. 

However, these stats can help us to understand the distribution of data across partitions. Therefore, it seems a good idea to log them at the time of cbcollect in couchbase.log so that we do not flood the indexer logs but can get the data distribution across partitions.