Cosmos: Warn when the partition key is given via both WithPartitionKey() and the predicate

We support two ways to specify the partition key: via WithPartitionKey() and via the predicate (Where).

The user may use both means in the same query; either the values are uselessly repeated (the query should be cleaned up), or worse, they're not, and then the query is guaranteed to never return any results. We can warn about this case.