[SB][Notifs] Add PromotedNotificationsProvider to auto-promote notifs.

PromotedNotificationsProvider is an interface with a single method,
`shouldPromote(entry: NotificationEntry): Boolean` that lets us
tell which notifications should be promoted. In AOSP, it just promotes
notifications with the FLAG_PROMOTED_ONGOING flag set.

Bug: 364653005
Flag: android.app.ui_rich_ongoing
Test: atest ActiveNotificationsInteractorTest
PromotedNotificationsProviderTest

Change-Id: I1913b65c79eb5a668a2f34e4ed2706595aed97f1