Show status bar notification icons on all displays

Since Android Views can only have one parent, we need to duplicate
the StatusBarIconView for each display.

The chosen approach is to create a multi display version of the
NotificationIconViewStore, that asks IconManager to create and update
icons.

We still keep the icons for the default display in the same place as
before (IconPack in NotificationEntry), to avoid having to refactor
things too much.

Test: MultiDisplayStatusBarNotificationIconViewStoreTest
Test: More to come when approach is approved
Bug: 369337701
Flag: com.android.systemui.status_bar_connected_displays
Change-Id: I779b2d39939e44d0544c496d46fc148e9fb65c36