Fixes for multirange selectivity estimation
* Fix enumeration of the multirange operators in calc_multirangesel() and
calc_multirangesel() switches.
* Add more regression tests for matching to empty ranges/multiranges.
Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/c5269c65-f9
Fixes for multirange selectivity estimation
* Fix enumeration of the multirange operators in calc_multirangesel() and
calc_multirangesel() switches.
* Add more regression tests for matching to empty ranges/multiranges.
Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/c5269c65-f9
