Reorganize tests and benchmark scripts.

Mainly to get rid of one top level directory. But this will
also be useful when there are tests of the embedding API.

test/language/class/syntax.wren

@@ -0,0 +1,11 @@
+// Empty body.
+class A {}
+
+// Newline body.
+class B {
+
+}
+
+// No newline after last method.
+class C {
+  method {} }