Move /src/test to /tests

tests/ui/async-await/nested-in-impl.rs

@@ -0,0 +1,15 @@
+// Test that async fn works when nested inside of
+// impls with lifetime parameters.
+//
+// check-pass
+// edition:2018
+
+struct Foo<'a>(&'a ());
+
+impl<'a> Foo<'a> {
+    fn test() {
+        async fn test() {}
+    }
+}
+
+fn main() { }