Add a new FrameBuffer class to describe memory used to store frames. This change just adds the new interface, future patches will migrate all parts of libcamera to use this and replace the old Buffer interface. This change needs to specify the const keyword for Plane::length() as to not get Doxygen confused with FrameBuffer::Plane::length added in this change. Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>