android: post_processor: Consolidate contextual information

Save and provide the context for post-processor of a camera stream
via Camera3RequestDescriptor::StreamBuffer. We extend the structure
to include source and destination buffers for the post processor, along
with CameraStream::Type::Internal buffer pointer (if any). In addition
to that, a back pointer to Camera3RequestDescriptor is convenient to
get access to overall descriptor (status, metadata settings etc.).

Also, migrate CameraStream::process() and PostProcessor::process()
signature to use Camera3RequestDescriptor::StreamBuffer only. This
will be helpful when we move to async post-processing in subsequent
commits.

Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>

src/android/camera_stream.h

@@ -121,9 +121,7 @@ public:
 	libcamera::Stream *stream() const;
 
 	int configure();
-	int process(const libcamera::FrameBuffer &source,
-		    Camera3RequestDescriptor::StreamBuffer &dest,
-		    Camera3RequestDescriptor *request);
+	int process(Camera3RequestDescriptor::StreamBuffer *streamBuffer);
 	libcamera::FrameBuffer *getBuffer();
 	void putBuffer(libcamera::FrameBuffer *buffer);