Disallow usb access to camera and mic devices if global privacy toggle is active

Note that this will not prevent currently running apps from accessing
usb devies to which a connection has already been established.
Removed isCameraDevicePresent() as this has been implemented as well in
UsbDevice#getHasVideoCapture().

Bug: 189915399
Test: Install nExt Camera - USB app, verify that camera is not accessible when camera privacy toggle is disabled.
Change-Id: Ie60adfe9fc667d883ad4a6b8d7582a4bc17d1549
Merged-In: Ie60adfe9fc667d883ad4a6b8d7582a4bc17d1549
(cherry picked from commit f063780d)