Re-land "Limit the number of concurrently snoozed notifications" am: 19032530

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/19347838



Change-Id: I5be9b3fb9f92771ec58081a909027c0917e87795
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>