SELinux: split service_contexts into platform and non-platform components.

Bug: 33746484
Test: Successfully boot with original service and property contexts.
      Successfully boot with split serivce and property contexts.

Change-Id: I6fec8d9b3023de09d69198c9e72311a1f03fe844
Signed-off-by: Sandeep Patil <sspatil@google.com>