Update aad o365group get so that it returns only O365 groups, rather than all groups

The current behavior might be confusing and lead to undesired effects if you think that you're working with an O365 group while in fact you're not.

Originally posted by @martinlingstuyl in #3786

Remarks

This item will be implemented when v7 is shipped, because it changes the workings of the command and existing scripts might break on this.