Add cross-app notification cooldown

 Add a new cooldown strategy that applies to all notifications
  across apps.

 Adjust the original cooldown strategy to apply to all notifications
  per app instread of per channel. Except for channels that have
  user-set sounds.

 Adjust cooldown timers to: t1=60 seconds and t2=5 seconds.

Test: atest NotificationAttentionHelperTest
Bug: 270456865
Change-Id: I1a536c48d4cd9285aa0446d9f630e82667418f9d