Add hasSentValidBubble to NotificationManagerService

If apps have conversations but not bubbles, we still show bubble settings
for them which is confusing for users. This change exposes whether an app
has sent a notification with valid bubble metadata, this allows us to hide
the setting until a bubble is actually sent.

If the app directs the user to bubble settings via the public intent,
they are still available.

Test: atest PreferencesHelper
Bug: 178387292
Change-Id: I7d3d92df49e7f4ed1d2c05cbba5f6f7786789d32