AAPT: Auto-alias application adaptive-icon

When a developer specifies an adaptive application icon,
and a non-adaptive round application icon, create an alias
from the round icon to the regular icon for v26 APIs and up.

We do this because certain devices prefer android:roundIcon over
android:icon regardless of the API levels of the drawables set for
either.

This auto-aliasing behaviour allows an app to prefer the
android:roundIcon on API 25 devices, and prefer the adaptive icon on
API 26 devices.

An app developer can override this behaviour by explicitly setting the
android:roundIcon to a drawable that has a v26 qualifier.

Bug: 34829129
Test: manual
Change-Id: Iaaaa5d8367e4f3f9e9f2e3b51c782d3be6a3bb71