Merge "Disallow system apps to be installed/updated as instant." into udc-dev am: 4c390bd2

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/25715830



Change-Id: I0f3d9c5f624e9d77ae1d695e216ff4896e4ae729
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>