Allow COPE admin to control screen configuration

Allow COPE admin to change screen configurations via
DPM.setSystemSetting and block user changes with
DISALLOW_CONFIG_BRIGHTNESS and DISALLOW_CONFIG_SCREEN_TIMEOUT

Bug: 323894620
Test: ScreenConfigTest
Test: ManagedProfileTest
Test: MixedDeviceOwnerTest#testSetSystemSetting
Test: ManagedProfileTest#testParentProfileApiDisabled
Test: ManagedProfileTest#testCannotCallMethodsOnParentProfile

Change-Id: I0c8e18e880da93006b52d28ba787c8e6968ff559
5 files changed