Cosmos: Detect partition key filters in more queries

Currently one needs to write the query like this to use a partition key:
```C#
var blogs = context.Blogs.WithPartitionKey("1337").ToList();
```

Instead we could automatically detect the partition key filter if used:
```C#
var blogs = context.Blogs.Where(b => b.PartitionKey == "1337").ToList();
```