Add ability to sort text modules by group


A while back I filed a bug report for not being able to sort text modules by groups (Status code 500 when trying to sort by groups in text module management · Issue #3494 · zammad/zammad · GitHub).

The fix for this was to remove being able to attempt to do so, however I think it would be handy to be able to sort this list by groups, as we use groups to handle several languages for customers, where each group has their own text modules translated. Without this sorting option, all text modules are shuffled together with various languages one after another.