13450 merge 12267_new_flow and update to new flutter version

pubspec.lock

@@ -1,5 +1,5 @@
 # Generated by pub
-# See https://www.dartlang.org/tools/pub/glossary#lockfile
+# See https://dart.dev/tools/pub/glossary#lockfile
 packages:
   async:
     dependency: transitive
@@ -61,7 +61,7 @@ packages:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.1.7"
   path:
     dependency: transitive
     description:
@@ -166,5 +166,5 @@ packages:
     source: hosted
     version: "3.2.3"
 sdks:
-  dart: ">=2.0.0 <3.0.0"
+  dart: ">=2.2.2 <3.0.0"
   flutter: ">=0.1.4 <2.0.0"