Limit the number of concurrent notifs appear on screen am: abe9246caa am: 273df63430 am: 86887fcb9a

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/15531757

Change-Id: I6cf45299e7387c68637145195ddbbd2500e2c1cf