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: I7e5134553e0f84531468482007b3ac9f85b8da3f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>