This commit updates the code which computes the dict for
setting groups mapping named user groups to ID and anonymous
groups to UserGroupMembersDict. After the changes, the dict
contains only anonymous groups values and the setting values
for group IDs not present in dict will be computed based on
the fact that those are named user groups.
This is a preparatory refactor for optimizing computing group
setting values for register response by fetching all anonymous
groups membership data just once.
bc2afd45b3