Transcoder: change src/dst to fd

MediaTranscoder takes fd as input from upper level service.

Also, leave file delete to client, since service side can't do file
create/delete. File opening is done by a callback into the app;
it seems delete should just handled by app side itself.

Minor refactor to reduce header pollution when included.

bug: 154734285
bug: 156003955, 152091443, 155918341
test: transcoder unit tests.

Change-Id: I4eb8a7d9fea2ccb479f09888353ac4e65bac16f8
diff --git a/media/libmediatranscoding/transcoder/tests/TrackTranscoderTestUtils.h b/media/libmediatranscoding/transcoder/tests/TrackTranscoderTestUtils.h
index 79c227b..32a1a0a 100644
--- a/media/libmediatranscoding/transcoder/tests/TrackTranscoderTestUtils.h
+++ b/media/libmediatranscoding/transcoder/tests/TrackTranscoderTestUtils.h
@@ -15,6 +15,7 @@
  */
 
 #include <media/MediaTrackTranscoder.h>
+#include <media/MediaTrackTranscoderCallback.h>
 
 #include <condition_variable>
 #include <memory>