libcamera: pipeline_handler: Return unique_ptr from generateConfiguration()

The PipelineHandler::generateConfiguration() function allocates a
CameraConfiguration instance and returns it. The ownership of the
instance is transferred to the caller. This is a perfect match for a
std::unique_ptr<>, which the Camera::generateConfiguration() function
already returns. Update PipelineHandler::generateConfiguration() to
match it. This fixes a memory leak in one of the error return paths in
the IPU3 pipeline handler.

While at it, update the Camera::generateConfiguration() function
documentation to drop the sentence that describes the ownership
transfer, as that is implied by usage of std::unique_ptr<>.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/pipeline_handler.h

@@ -48,7 +48,7 @@ public:
 	bool acquire();
 	void release();
 
-	virtual CameraConfiguration *generateConfiguration(Camera *camera,
+	virtual std::unique_ptr<CameraConfiguration> generateConfiguration(Camera *camera,
 		const StreamRoles &roles) = 0;
 	virtual int configure(Camera *camera, CameraConfiguration *config) = 0;