modules/{output,files,test}: move outputs to build scope

Move the following output options into `build`:
- finalPackage -> package
- printInitPackage
- initPath -> initFile
- filesPlugin -> extraFiles
- test.derivation -> test

wrappers/nixos.nix

@@ -49,8 +49,8 @@ in
 
   config = mkIf cfg.enable {
     environment.systemPackages = [
-      cfg.finalPackage
-      cfg.printInitPackage
+      cfg.build.package
+      cfg.build.printInitPackage
     ] ++ lib.optional cfg.enableMan self.packages.${pkgs.stdenv.hostPlatform.system}.man-docs;
 
     environment.variables = {