Add new enforceUniqueness to refineCollectionShardKey command

(Analogous to SERVER-63732 but for the refineCollectionShardKey command. An implicitlyCreateIndex parameter isn't relevant for refineCollectionShardKey because the command won't attempt to create an index even when the collection is empty.)

enforceUniqueness defaults to true and when set to false, ignores uniqueness property when validating indexes for refineCollectionShardKey.

Regardless of both settings, refineCollectionShardKey should still return an error if there are no index that is compatible with the new shard key pattern.