Start IoT System Service from SystemServer

For feature type "embedded", launch IoTSystemService from
System Server.

Test: Wrote a IotSystemService and ensured that the service is
successfully started on an iot device.

Bug: 67641069
Change-Id: I5aa0408f35fb4a5b0787cf9b20454720d8ae130f
Cherry-picked and refactored from oc-iot-dev branch