[BUGFIX] CategoryCollection must handle multiple relations

Since #51921 it is possible to have multiple fields for defining
relations to categories. The CategoryCollection and the
categories-based page menu are now adapted to handle this correctly,
instead of retrieving records for relations defined in all fields.

Resolves: #52285
Documentation: #52302
Releases: 6.2
Change-Id: I156528669704004a86243e03f34d3a1af07cdb21
Reviewed-on: https://review.typo3.org/24066
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Fabien Udriot
Tested-by: Fabien Udriot
Reviewed-by: Francois Suter
Tested-by: Francois Suter