Moves DeviceState from the server to the client side.

Moving the DeviceState class to the client side allows us to use this
class on both sides, which can allow us to give more information to
the client instead of just the state identifier.

Bug: 293636629
Test: DeviceStateTest
Change-Id: Ib05b36889db45f3cc9027d66f4bf8f1d528592c9