libcamera: object: Create parent-child relationships

Add a parent Object to Object instances, and track the parent-children
relationships. Children are bound to the same thread as their parent,
and moving an Object to a thread automatically moves all its children.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/include/thread.h

@@ -61,6 +61,8 @@ private:
 	friend class ThreadMain;
 
 	void moveObject(Object *object);
+	void moveObject(Object *object, ThreadData *currentData,
+			ThreadData *targetData);
 
 	std::thread thread_;
 	ThreadData *data_;