R1:51c4b199d027

Allow policy-aware queries to prefilter results

Summary:
Provides a simple way for policy-aware queries to pre-filter results without needing to maintain separate cursors, and fixes a bunch of filter-related edge cases.

- For reverse-paged cursor queries, we previously reversed each individual set of results. If the final result set is built out of multiple pages, it's in the wrong order overall, with each page in the correct order in sequence. Instead, reverse everything at the end. This also…