Need a way to collect CBO stats for all indexes for a collection, and for a scope

Stats has to be collected per index. This can be also achieved with a sub query 

UPDATE STATISTICS FOR <collection> INDEX((SELECT RAW name from system:indexes 
    WHERE state=‘online’ AND keyspace_id=‘<collection_name>’ AND bucket_id=‘<bucket_name>’ AND scope_id=‘<scope_name>’ AND `using`='gsi'))

We should allow users to issue: 

UPDATE STATISTICS FOR <collection>;

UPDATE STATISTICS FOR <scope> ;