Track bubbles that were whitelisted & blocked, don't bubble blocked ones

The experiment to whitelist packages to auto-bubble doesn't allow you
to specify specific notifs to be blocked (you can longpress on the notif
and change it but it won't work). This CL fixes that behaviour by tracking
when a user blocks one of these.

Bug: 145763712
Test: manual:
      1) In people version of test app, disable bubble metadata
      2) adb shell settings put secure allow_message_notifs_to_bubble 1
      3) adb shell settings put secure whitelisted_auto_bubble_apps com.google.android.samples.bubbles
      4) double tap on each person in test app to produce notifs
         => notice they are all bubbles
      5) longpress on a notif and put it to "alert" instead of bubble
         => notice that that bubble is removed from stack if it was there
      6) get notif from person you blocked
         => it does not bubble
      7) longpress on that notif to "bubble" it again
         => it bubbles
      8) dismiss stack & get new notif from that person
         => it bubbles

Change-Id: I89977fa63d7581c83d539af76e4e70ae82737cbf