Convert device state sensor type from int to String.

This converts the sensor type within the device state config file from
a raw int type to its fully qualified Sensor string type. For ex, a hinge
sensor that was previously identified with "36" would now be identified
with "android.sensor.hinge_angle".

Bug: 159401801
Test: atest DeviceStateProviderImplTest
Change-Id: I32ff9db11f68d602f7084d5308f0435bf418e522