Box-Art Reimplementation

[NightScript370]

Is your feature request related to a problem? Please describe.
Seeing a bunch of question-mark box art is not pleasant on the eyes when there aren't any box art images. However, the recent commit which disabled it means that it now receives a ton of less exposure.
Also, cached box art just cache's everything in the beginning, even if it's a ROM icon that doesn't need to be loaded. At the same time, though, there's already a progressive loading system for the icons on the touch screen we could just plug in.

Describe the solution you'd like

• Get rid of the questioned box art icon for the DSi-based themes (this isn't trying to exclude the other themes, since they don't have any box art but rather, it's trying to exclude the DS Classic Menu, which for the time being has nothing on the top screen. Once the clock gets implemented, then get rid of box art from there). We already have a picture that should be seen, so why overlay that?
• Get rid of the dedicated box art pre-load option. While it isn't a bottleneck when navigating the ROMs, it's an annoying bottleneck when loading the folder, especially considering it's loading the boxart for options that will not even be navigated. Instead, just use the same system used for icons to load box art for DSi systems
• Revert the commit that disabled it by default. If it's not a disturbance, why remove?

Describe alternatives you've considered
Change the default to be based on files existing or not. I suggested that but now I disagree; if people didn't set up twilight well before, they would still be unaware

Additional context
Might need ways to make it so that box art is loaded for some icon entries and not to others.