Cosmos: Improve single-partition queries

[AndriySvyryd]

Lift the partition filter for joins and other queries as needed

[roji]

@AndriySvyryd what did you have in mind here that isn't covered by #20350? Should this one be closed as a dup of that?

[AndriySvyryd]

This is about inter-document queries within the same partition. Basically we should make sure that all partition filters in the same query are collapsed

[roji]

OK, since this is about inter-document queries - which we don't support - I'll move this to the backlog.