Improve debug prints in InputDispatcher

It's useful sometimes to print out the events produced by the
dispatcher. In this CL:
- Switch (partially) to the C++-style prints from android-base
- Add a way to print keyevents, motionevent into a stream
- Add InputEventInjectionResult print

Also, improve the debug prints for outgoing events. When an entry is
getting dispatched, the dispatcher may modify its action, among other
variables. With this CL, this will be observable in the logs.

Bug: 211379801
Test: atest AccessibilityEndToEndTest
Change-Id: I221161af7903ae4da77733265c67a426a3e5b557