The goal of this task is to clear the Collection Sharding State map (i.e. all collections) during the setFCV upgrade to 6.0.

The reason to do that is to define a barrier from which all shards must know what they own at all moment. We can do this because since 5.3 we introduced a new migration protocol that guarantees that both donor and recipient update their filtering information as part of the commit phase. Before that, we had a weaker guarantee: the donor for sure knew about the migration but for the recipient we just triggered a best-effort refresh.

This change should land on 6.0.