Improve group/module bar layout in Doxygen pages

### Description

When a class belongs to numerous modules/groups, the group/module links become a little bit cluttered, e.g.


The layout should be improved for better understanding the module/group membership of a given class.

### Expected information

Group and module names should be better separated/organized in the group/module bar.

### Actual information

Group and module names become cluttered; one does not really know which one is a module/group.

### Versions

`master`

### Additional Information

Slightly related to #3656.