Fix issue where ScanFilterAndProject with PageSource might skip data

This can happen when processing the last page due to a broken check
in the isFinished() method. The implementation needs to check whether
there's a partial page pending processing before indicating the operator
is done.
Disable optimized readers by default
Add session property to enable Hive optimized readers
Expand UNNEST documentation
Add UNNEST to Hive migration guide
Fix unnesting nested arrays/maps
Update release notes