Partition the targets for notice files.

Partition the targets into those appearing in system images, those
appearing somewhere unreadable by the Settings UI, whose notices
must appear in a readable system image, and those not appearing
on the device thus not needing notices. Assert no other targets
appear under $(PRODUCT_OUT).

Test: manually built and tested phone image

Change-Id: If82cb36f98f8e6066d1c67bb4d15976be433d403