Missing ARIA roles and attributes for colgroup and rowgroup

[JAWS-test]

Description of bug or feature request

I can define rowgroups and colgroups in HTML. With ARIA only rowgroups.

In HTML I can label the rowgroups and colgroups with scope=rowgroup and scope=colgroup. In ARIA, I can explicitly label the rowgroup using aria-label or aria-labelledby, but I cannot assign the role of a group label to the respective table cell, as columnheader and rowheader only serve as labels for column and row respectively.

This is important for complex tables. See: https://www.w3.org/WAI/tutorials/tables/multi-level/

Will this require a change to CORE-AAM?

I don't know. Related: w3c/html-aam#474

Will this require a change to the ARIA authoring guide?

No, but it would be good to show how complex tables can be implemented well