CEC: Add logic to return to internal source

This CL introduces a logic that, upon receiving <Inactive Source>
from the active source or a corresponding MHL subcommand, lets
the service return to one of internal inputs.

Introduced to handle it is a new type for HdmiDevice (INACTIVE)
that will be passed to input change listeners. The callback
is expected to transform to other mechanism such as intent,
to let TV app to decide which input to switch to, which will
be one of non-HDMI input that was viewed previously.

Bug: 19008579

Change-Id: I1922f4cd20e9220411061bb9d9fbe5fbc5676d48