Separate mapfs, sprites, etc used by splat from those used at build time

[bates64]

This currently is a cause of some weirdness when modding. For instance if I change mapfs.yaml to rename an asset, splat will split the asset at that index to the new name and put it in ver/us, which it almost certainly shouldn't. For all mods, ver/us should split the same way.

TBH this should apply to all of splat.yaml - mods should use their own splat.yaml. Perhaps this is a problem for dx?

Related to #1170

[z64a]

For dx, I plan to extract the map table to an xml asset and generate the c arrays during build.