Migrate FocusEventDebugView to an input subpackage.

This CLs migrates FocusEventDebugView to a subpackage of "com.android.server.input". This subpackage will be used to keep debugging-related code. This CL also moves the rotary input visualization views into separate files in the same subpackage.

Note: I've tried to mark FocusEventDebugView.java and FocusEventDebugViewTest.java
as renamed, but it didn't work. Compare patches 7 and 8 to see line
changes in those files.

Bug: 286086154
Test: atest FocusEventDebugViewTest RotaryInputGraphViewTest RotaryInputValueViewTest
Change-Id: Ica004656a99447818a47b63e2a50c15744039abf