stage1's got prepare-modules target collecting
modules file snippets all over stage1/modules.d/
subdirectories within individual features.

stage2 now adds names of all the features going into
a particular image as snippet file suffix list so that
individual features don't have to register themselves
twice (as a feature and as a propagator modules.d
snippet carrier).

This is going to allow both "uncommon" modules getting
included with no problem (sin@ has wanted cifs ones
for quite some time, for example, and some want e.g.
infiniband modules) *and* to reduce the actual list
below the common mark as well (which is the case with
live-privacy image, for one).

And stage1 memory consumption does matter in some cases
as it's highly critical with no chance to use swap yet.