Clean up the root of the class/metaclass hierarchy.

test/class/type.wren

@@ -0,0 +1,10 @@
+class Foo {}
+
+// A class is a class.
+IO.write(Foo is Class) // expect: true
+
+// It's metatype is also a class.
+IO.write(Foo.type is Class) // expect: true
+
+// The metatype's metatype is Class.
+IO.write(Foo.type.type == Class) // expect: true