Move mojo and mojom from mojo/public/dart to mojo/dart/packages

mojo/dart/packages/BUILD.gn

Index: mojo/dart/packages/BUILD.gn
diff --git a/mojo/public/dart/BUILD.gn b/mojo/dart/packages/BUILD.gn
similarity index 58%
copy from mojo/public/dart/BUILD.gn
copy to mojo/dart/packages/BUILD.gn
index eb711461d174f58947bec8707176a7901189d541..ddcbf7166ff0102a567c0898fe7978a367b5d695 100644
--- a/mojo/public/dart/BUILD.gn
+++ b/mojo/dart/packages/BUILD.gn
@@ -2,10 +2,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-group("dart") {
+group("packages") {
   deps = [
-    "mojo",
-    "mojom",
-    "third_party",
+    "//mojo/dart/packages/mojo",
+    "//mojo/dart/packages/mojo_apptest",
+    "//mojo/dart/packages/mojom",
   ]
 }