[Notifications] Notify NotifCollectionListeners when a pending entry has

been removed.

The NotifCollectionListener (listener for the new pipeline) specifies that #onEntryRemoved should
be called when a notification has been cancelled, regardless of whether
or not it has been inflated. This CL adds a call to that method to
ensure that specification is met.

Test: atest + New unit tests
Fixes: 201097913
Change-Id: I337e5a942b1f46b51102a698dad90fbfa82d66ca