Separate device and product overlays

This change adds book-keeping of whether an overlay came from
DEVICE_PACKAGE_OVERLAYS or PRODUCT_PACKAGE_OVERLAYS. This is
later used when writing the output to soong_app_prebuilt.mk, to
use either LOCAL_SOONG_[DEVICE|PRODUCT]_RRO_PACKAGES depending
on the original source.

This change is intended to be a noop on its own, but allows a
follow-up make change to customize the location of the auto-generated
RRO packages.

Bug: 127758779
Test: verify noop on presubmit targets
Change-Id: Ib24fe1d05be132c360dd6966f7c83968c9939f77