primary feed support for replication streams

This starts to matter if you're trying to have cbgt manage primary datasources like vbuckets.

We have the existing PrimaryFeed, where PrimaryFeed's can be configured for NumPartitions.

But, it's unaware of replication.

So, if a pindex X has source partitions 17 (i.e., vbucket 17), when run on a master node M, the PrimaryFeed does the right thing and behaves like a nil feed. When run on a replica node R, the PrimaryFeed should (new proposed functionality) try to setup replication streams (like DCP) to master node M.

Be sure to consider takeover streams, too.

The issue does not name files or tests; begin by locating the existing PrimaryFeed and the code that handles replication or DCP streams. Trace how source partitions behave on master and replica nodes, including takeover streams. Done means replica PrimaryFeeds establish the required streams while master behavior remains unchanged; note that this repository has moved elsewhere.

Written by the indexing model from the issue text.