DO NOT MERGE Filter out suppressed notifications in entry manager

`NotificationEntryManager#hasActiveNotifications` used to be in 1:1
correspondence with the visible notifications in the shade, and as such
was suitable for code that needs to do things like calculate the height
of the shade. However if there is a bubble, it's still backed by a
notification but is suppressed from the shade.

This CL is unfortunately hacky because the API for
NotificationEntryManager doesn't have the concept of "a notification
which exists but is not in the shade" and therefore the correct fix
actually would involve creating the correct api and updating all call
sites with the correct semantics.

Test: manual
Bug: 161461739
Change-Id: I9b0fc0f48609b64371d3cb7677228b4bb1fa6aef