Convert remaining item color lists into palette textures

[yel0h]

Finishes the migration started in #3403 and #3460.

Removed the legacy .colors parsing fallback in Material.init and helpers. loadColorsFromTexture now always resolves a color source instead of returning a .notLoaded status for the caller to fall back on. Missing .colorTexture field, failed load, or invalid image (too small or with non-opaque outline pixels) all log an error and fall back to graphics.Image.defaultImage.

Closes #3451

[IntegratedQuantum]

Also for completeness, would you mind sharing the script you used for conversion? It would be handy if someone searches for something similar in the future.

[IntegratedQuantum]

Instead of all this complex logic for handling the default image and error printing, I'd suggest to use errors to simplify the process:

1. Change the return value to !void
2. at the callsite handle the error by setting some default colors:

catch |err| {
    std.log.err("Could not load material colors for item {s} from paths {s} and {s}: {s}", .{self.id, path1hhawehu, path2dwdhihawdhuw, @errorName(err)});
    self.outlineColorLight = 0xff00ff;
    self.outlineColorDark = 0x000000;
    self.colorPalette = &.{0xff00ff, 0x000000, 0xff00ff, 0x000000};
};

3. all error cases in here can be replaced with a simple return error.@"MissingAttribute: colorTexture" or return error.@"Color texture must be at least 2×2 pixels" or return error.@"Colors must be fully opaque"

[yel0h]

Sure, here's the script: https://gist.github.com/yel0h/d9ccbdf51c59e3915feceff490024872