Add device admin restrictions for mic/cam toggles

Introduces DISALLOW_CAMERA_TOGGLE and DISALLOW_MICROPHONE_TOGGLE
which are Device Owner restrictions to prevent the user from
turning off global camera & microphone access on a fully-managed
device.

Test: atest DeviceOwnerTest#testSensorToggleRestriction
Test: atest UserRestrictionsTest
Bug: 184927615
Change-Id: I500f1283689497812bd2df606e35abe6d9d91c61