Add CtsShimAddApkToApex app

CtsShimAddApkToApex app is a simple app with one activity.
It will be used in a cts to test updating the shim apex with a new
version which contains this app then the test will verify that it can
start the app contained in the apex.

Bug: 289535527
Test: m CtsShimAddApkToApex
Change-Id: I98dbe9906e9705cc736269ddca947fd94d23eb81