Remove core.mk.

It only has one mk inheriting it now, so it's redundant. Push its
packages into the single child (generic_no_telephony.mk).

Bug: 80410283
Test: diff product variables with multiproduct_kati
Change-Id: Ie56e22be7f43558fdd259c808e5a6a937bd12ea6
Merged-In: Ie56e22be7f43558fdd259c808e5a6a937bd12ea6
(cherry picked from commit d0d862d7)