Add new filter operator "Is not equal to OR is empty"

See ✨ Views UI should offer a 'Treat NULL values as FALSE' on boolean field filtering to expose the already existing code path for handling this Needs work for the boolean version of this request.

See https://www.drupal.org/project/field_defaults → for what I feel is the correct solution for this that works for all field types and takes the actual default value of a field into account

See https://www.drupal.org/project/field_defaults → for what I feel is the correct solution for this that works for all field types and takes the actual default value of a field into account

If I understand correctly, that will only work if all result items have that field. Not in cases where that field is not present on any of the other content types. I think #2769407 will fix that somewhat.