[Feature] Add Configurable Horizontal and Vertical Scaling, as Well as Scaling Layers

[GK6475]

It would be nice to be able to toggle different kinds of scaling for horizontal and vertical aspects of the image. Say, for instance, a game or console interpolates its horizontal pixels to a non-integer value. It would be nice to be able to do vertical integer scaling and horizontal bilinear to achieve a potentially better image overall. It would also be nice to have scaling layers, one for blending pixels and another to scale to fit to a resolution like 1080p. It would also be really nice to be able to adjust the strength of each scaling method, to suit the user's purposes, sort of like RetroArch with its ablility to apply configurable scaling layers.