Finish migrating to BroadcastDispatcher

This CL migrates most of the remaining classes to use
BroadcastDispatcher. Some classes left are Views or created before the
BroadcastDispatcher can be injected.

Adds docs for instructions on using the BroadcastDispatcher.

Using the broadcast dispatcher, the time system_server spends
dispatching common intents to SystemUI like SCREEN_OFF and SCREEN_ON can
be seen to decrease from ~70-150ms (in a Q build) to ~2-4ms.

Additionally, once a broadcast is received by the dispatcher, time
until it is fully dispatched inside SystemUI is not impacted greatly.
Most broadcasts are fully dispatched after ~20ms with a few of them
taking ~100ms.

Test: atest SystemUITests no regressions
Test: build and boot
Test: tried some random broadcasts and they are properly dispatched
Test: BroadcastDispatch dump
Test: adb shell dumpsys activity broadcasts
Bug: 134566046

Change-Id: I26a592be66b053f25669b5481b58bf7f07bfd0da