Abstract away access to audio streams HAL in AudioFlinger

In this CL all direct access to audio_stream_t, audio_stream_out_t, and
audio_stream_in_t their functions is encapsulated within the new
hierarchy of Stream[In|Out]HalLocal classes.  AudioFlinger uses
interface classes Stream[In|Out]HalInterface to access these functions.

Note that NBAIO still receives raw HAL stream handles and needs to be
converted separately.

Bug: 30222631
Test: manual with Loopback app

Change-Id: I6388cfa2006791c9c0aa7bb186719209726a2d48