Rename cancelRequest API to cancelStateRequest and remove the

request parameter

With the change to only having one override request at a time,
we can simplify the cancelRequest API in DeviceStateManager
to not require a request object and have the current
override request canceled. This API is still gated
around having the CONTROL_DEVICE_STATE permission or being the
top level app.

Bug: 215400374
Test: DeviceStateManagerGlobalTest, DeviceStateManagerServiceTest &&
 OverrideRequestControllerTest
Change-Id: I565b608372c21384d401db502b16553ed85b86ee