Rotating sprites/backgrounds look terrible when scaled

[ZironZ]

This is caused by the whole-scene 2D scaling just upscaling the already rotated low resolution image.

To make it look correct we need to scale all the sprites/background before they are rotated, and then do all the rotations at a higher resolution.

How Mario Kart currently looks with whole-scene 2D scaling (NNEDI3):

How it looks in melonDS with 4x internal resolution and no scaling:

[ZironZ]

Here is a prototype that does all the rotations at a higher resolution (also NNEDI3):

This prototype looks quite a bit better in motion. However, its performance becomes more like texture scaling since we are individually scaling up a lot of elements in the scene. It also has more chances to look slightly "off", since we are compositing everything together at a higher resolution. You can end up having weird little 1 pixel gaps when say a character portrait is placed onto a UI background.

Once I have the prototype working better I plan to add a toggle that says something like "High-quality Rotated Sprites" to enable this version of the scaling. I'll also have an advanced option to just use melonDS's nearest neighbour behaviour instead, since this type of scaling has a decent chance of breaking things.