[BP to Alice] FTS - GetTaskList timeout during rebalance with numerous index aliases

During a rebalance operation, fts tries to compute the number of index partitions to be moved/rebuilt using the function getMovingPatitionsCount here - https://github.com/couchbase/cbgt/blob/mad-hatter/ctl/ctl.go#L190. 

But when there are lots of index aliases, it can cause an un necessary delay in the bucket detail fetching operations happening inside this utility function. For index aliases, there is no reason to fetch the source bucket details as the aliases are always built on other indexes as their sources and not on buckets directly.

This futile source bucket fetch attempts can cumulatively increase the overall execution time for the getMovingPatitionsCount function which can cause higher level timeouts like GetTaskLists.