Add TimeZoneDetector.suggestManualTimeZone() to set the time zone
"manually" and switch the device policy manager code over to using
it.
Add RequiredPermission annotations to TimeZoneDetector while there.
Bug: 140712361
Test: treehugger only
Test: atest services/tests/servicestests/src/com/android/server/devicepolicy/DevicePolicyManagerTest.java
Change-Id: Id247fddfdd793732dd88294ee215eda37cd0be4c