Revert changes to core SDK members that haven't been propagated to the g3 SDK yet (#18654)

* Revert changes to core SDK members that haven't been propagated to the g3 Dart SDK yet.

* Respond to comments.

* Remove retype

* Temporarily un-remove VMService.retype to unblock g3 roll

* Checkout back to master, we need fewer changes to reach compat with dev.61 than dev.60

packages/flutter_tools/lib/src/vmservice.dart

@@ -1395,6 +1395,7 @@ class ServiceMap extends ServiceObject implements Map<String, dynamic> {
   Iterable<MapEntry<String, dynamic>> get entries => _map.entries;
   @override
   void updateAll(dynamic update(String key, dynamic value)) => _map.updateAll(update);
+  Map<RK, RV> retype<RK, RV>() => _map.cast<RK, RV>(); // ignore: deprecated_member_use,annotate_overrides
   @override
   dynamic update(String key, dynamic update(dynamic value), {dynamic ifAbsent()}) => _map.update(key, update, ifAbsent: ifAbsent);
 }