Add a test to verify input disconnected when screen off

This is for CL[1] to verify input connection will be disconnected
when screen off (also verify input will connect when screen on).

Also, add some utility methods in TestUtils for IME tests:
- turnScreenOn
- turnScreenOff
- DisableScreenDozeModeRule for disabling Aod mode to make turnScreenOff
  state reliable.
- unlockScreen when device enabled keyguard.

[1]: Ic11956fe745a829da1ec7c09ea214e9b3961c8e0

Bug: 26851566
Bug: 141738570
Test: atest InputMethodStartInputLifecycleTest
Change-Id: Ib2bdb64312922c8495d1a60cfeb9fbaa98001fc7