Store the async-await compiled pub code directly in the repo.

sdk/lib/_internal/pub_generated/test/get/hosted/cached_pubspec_test.dart

+library pub_tests;
+import 'package:scheduled_test/scheduled_test.dart';
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+main() {
+  initConfig();
+  integration('does not request a pubspec for a cached package', () {
+    servePackages((builder) => builder.serve("foo", "1.2.3"));
+    d.appDir({
+      "foo": "1.2.3"
+    }).create();
+    pubGet();
+    getRequestedPaths();
+    d.cacheDir({
+      "foo": "1.2.3"
+    }).validate();
+    d.packagesDir({
+      "foo": "1.2.3"
+    }).validate();
+    pubGet();
+    getRequestedPaths().then((paths) {
+      expect(paths, isNot(contains("packages/foo/versions/1.2.3.yaml")));
+    });
+  });
+}