libcamera: request: Add operator<<()

With the recent addition of operator<<() in most libcamera core classes
to replace usage of the toString() function the Request class was left
behind.

Add operator<<() for the Request class and reimplement toString().

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/internal/request.h

@@ -44,6 +44,7 @@ public:
 
 private:
 	friend class PipelineHandler;
+	friend std::ostream &operator<<(std::ostream &out, const Request &r);
 
 	void doCancelRequest();
 	void emitPrepareCompleted();