Port device_generic_sensor to be hosted in Device Service.

services/device/manifest.json

 {
   "name": "device",
   "display_name": "Device Service",
   "interface_provider_specs": {
     "service_manager:connector": {
       "provides": {
         "device:battery_monitor": [ "device::mojom::BatteryMonitor" ],
         "device:fingerprint": [ "device::mojom::Fingerprint" ],
+        "device:generic_sensor": [ "device::mojom::SensorProvider" ],
         "device:power_monitor": [ "device::mojom::PowerMonitor" ],
         "device:screen_orientation": [ "device::mojom::ScreenOrientationListener" ],
         "device:sensors": [
           "device::mojom::LightSensor",
           "device::mojom::MotionSensor",
           "device::mojom::OrientationAbsoluteSensor",
           "device::mojom::OrientationSensor"
         ],
         "device:time_zone_monitor": [ "device::mojom::TimeZoneMonitor" ],
         "device:vibration": [ "device::mojom::VibrationManager" ],
         "device:wake_lock": [ "device::mojom::WakeLockContextProvider" ]
       },
       "requires": {
         "service_manager": [ "service_manager:all_users" ]
       }
     }
   }
 }