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

sdk/lib/_internal/pub_generated/test/get/switch_source_test.dart

+library pub_tests;
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+main() {
+  initConfig();
+  integration('re-gets a package if its source has changed', () {
+    servePackages((builder) => builder.serve("foo", "1.2.3"));
+    d.dir(
+        'foo',
+        [d.libDir('foo', 'foo 0.0.1'), d.libPubspec('foo', '0.0.1')]).create();
+    d.appDir({
+      "foo": {
+        "path": "../foo"
+      }
+    }).create();
+    pubGet();
+    d.packagesDir({
+      "foo": "0.0.1"
+    }).validate();
+    d.appDir({
+      "foo": "any"
+    }).create();
+    pubGet();
+    d.packagesDir({
+      "foo": "1.2.3"
+    }).validate();
+  });
+}