Add new shell commands for DeviceStateChanged CTS test

For the new CTS test for DeviceStateChanged metric we
need commands with simple outputs to determine the current
device state and the supported states.

Bug: 181542365
Test: flash device with framework changes then $ atest DeviceStateStatsTests
Change-Id: Icb2e755e258f8c3dba3aed34b37cdb7295df5434
1 file changed