AAPT2: Fix issue with resource deduping

Resource deduping relies on the definitions of
ConfigDescription.ConflictsWith, ConfigDescription.IsCompatibleWith,
and ConfigDescription.Dominates.

ConflictsWith is supposed to ignore range-based qualifiers, like
version, density, smallest width, screen size, etc.

This was not the case for screen size, and was assumed that the
choice of screen size is mutually exclusive.

This CL fixes the assumption and includes screen size (small, normal, large, xlarge)
as a qualifier that does not conflict.

Bug: 64397629
Test: make aapt2_tests
Change-Id: I573a6735fedd7721a10ba32902bc5d27ef99b88e