Handle device context with invalid deviceId

- Update documentation to clarify that deviceId of a context
  created with CreateDeviceContext() will not be updated even
  if the underlying device is closed/removed.
- Update isDeviceContext to return false in such a case as this
  is not a reliable ID anymore.

Bug: 265020871
Test: atest DeviceAssociationTest
Change-Id: I31857c58959c47dc3e2193df4bd5d4c9beba4676