Replace use of NotificationContainerBounds with a Float.

The way notification code handles bounds is currently hacky and unclear.  This is a tiny refactor to start reducing use of this type. It also reduces potential unnecessary recomputation of max notifications.

Bug: 296118689
Test: atest SystemUITests
Flag: ACONFIG com.android.systemui.migrate_clocks_to_blueprint TEAMFOOD
Change-Id: I4374b51eda1ce86bd57d0dcdc82f77b630230521