Reduce NICRefactor load on main dispatcher

Main thread load is reduced via three tacks:

1. Offload as much computation as possible to the bg thread dispatcher.

2. Share Flows where possible. This is performed in the view-binder
where we know that states will be observed by multiple collectors, so we
can optimize by sharing using stateIn.

3. Remove any unnecessary upstream Flows, to reduce excessive
recomputation.

Tracing has also been added to help diagnose future performance issues,
if any arise.

Bug: 317509049
Flag: ACONFIG com.android.systemui.notifications_icon_container_refactor TEAMFOOD
Test: atest SystemUITests
Change-Id: I90e1cfc3ab24c75ec15a1e14952b880829f17471