aaudio: cleanup FIFO

Remove unused methods and fields.
Better code format and alignment.
Use unique_ptr for mFifo.
Remove getFifoController() method that exposed pointer.
Updates tests and calling code as needed.

Test: test_atomic_fifo.cpp
Change-Id: I1ea66beaadeb74083307835858b757e4753affda
diff --git a/services/oboeservice/AAudioMixer.cpp b/services/oboeservice/AAudioMixer.cpp
index b031888..1c03b7f 100644
--- a/services/oboeservice/AAudioMixer.cpp
+++ b/services/oboeservice/AAudioMixer.cpp
@@ -99,7 +99,7 @@
         }
         partIndex++;
     }
-    fifo->getFifoControllerBase()->advanceReadIndex(framesDesired);
+    fifo->advanceReadIndex(framesDesired);
 
 #if AAUDIO_MIXER_ATRACE_ENABLED
     ATRACE_END();