[ASTERIXDB-2516][COMP] Change logical comparators handling of null/missing - user model changes: no - storage format changes: no - interface changes: no
Details: Change the result of comparing against null and missing. For arrays, comparing against null or missing item will result in incomparable. For records, comparing against a null field will result in incomparable. - modified test cases accordingly - moved few object factories to the common place. - modified compareRecords to avoid string construction for field names - few code clean-ups.