Use config groups stored in list items to save changes

Since the config group corresponding to a certificate category list item
is stored in the list items we don't have to make assumptions about a
one-to-one mapping between "Key Filter #NNN" groups and list items to
know which group to save a list items properties to. In particular, we
can simply skip CMS-specific filters if CMS is disabled instead of
creating hidden list items for them.

• GnuPG-bug-id: T8079