fix ADD_EXTRA_GROUPS regex and set EXTRA_GROUPS to those used by d-i
Source of groups used by debian-installer:
https://salsa.debian.org/installer-team/user-setup/-/blob/master/debian/user-setup-udeb.templates
Ideally, the groups suggested by adduser and those used by d-i should be the same. See https://bugs.debian.org/1012168