libcamera: media_object: Add MediaPad string representations

Facilitate easy representations of a MediaPad object by preparing
it as a string and supporting output streams.

A MediaPad will be report in the following style:

  'imx283 1-001a'[0]

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/media_object.h

@@ -71,6 +71,8 @@ public:
 
 	void addLink(MediaLink *link);
 
+	std::string toString() const;
+
 private:
 	LIBCAMERA_DISABLE_COPY_AND_MOVE(MediaPad)
 
@@ -85,6 +87,8 @@ private:
 	std::vector<MediaLink *> links_;
 };
 
+std::ostream &operator<<(std::ostream &out, const MediaPad &pad);
+
 class MediaEntity : public MediaObject
 {
 public: