In this ticket, we will make the flag gather a list of idle cursors, determined solely by whether or not they are pinned.

This is similar to what is done in the Proof of Concept except it will also add fields to GenericCursor which are already present on both ClientCursor and ClusterClientCursor

It also should not bother to include any cursor object in the 'inprog' ops for any getmore ops. This will happen later. This was attempted in the POC but we decided to do it a different way, namely by tracking a GenericCursor on the CurOp object during the getMore command.

This covers both mongos and mongod. Any fields that exist exclusively on mongod or exclusively on mongos should be excluded in this ticket.