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

Merge "Disallow system apps to be installed/updated as instant." into udc-dev am: 4c390bd2 am: 0ddf73b8 am: 08e094fa

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



Change-Id: Ic10c9f0661b1160287fe98cccb317f798f548f17
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>