Simplify handling activity config a bit

- Remove parameter movedToDifferentDisplay because it can be
  retrieved by comparing current display id and new id. Then
  some logic can be shared.
- REPORT_TO_ACTIVITY was used to distinguish whether to report
  new configuration to the activity according it is process or
  activity level change. Since the conditions had been separated
  by different methods, its usages can be removed.

Bug: 160780522
Test: atest MultiDisplayActivityLaunchTests
Change-Id: I914963261ba339ba8c7bb5c50d7a8b25791db12e