Reverse sorting on collections produces weird results with batching

[agitator]

Sorting reverse on a collection result displays items already shown in the next batch page and over.
Tested on Plone 5.2 and 6

Related to zopefoundation/Products.ZCatalog#81
and zopefoundation/Products.ZCatalog#108

Possible fix zopefoundation/Products.ZCatalog#82

Workaround: create your own index that is reversed by default