Implement suggestions for collection descriptors

[marcos-lg]

From this comment: #558 (comment)

If it's easier it can be a new type of suggestion just for descriptors (instead of a suggestion that includes both the collection and the descriptors).

Also, since the IH-sync now also creates suggestions we need to see how we fit there the descriptors that are created from IH(collection summary and important collectors). To make it easier we can skip the descriptor suggestions in the sync and they will be created in the next syncs when it updates the entity(so if the IH suggestion is applied it won't contain the descriptors at first but they will be created in a later sync).