Introduce PowerManager mock

Remove previous mocks of the IPowerManager interface.
Remove power-state-related stubs from HdmiControlService.
Stub of HdmiControlService#wakeUp needed to remain where we needed to
check if that method was invoked and that couldn't be infered from a
power state change.

Bug: 173108866
Test: atest

Change-Id: I29dbb3b50a1b86032bd7cdad1ec8717d305a2bca