Enforce use_key_in_widget_constructors and file_names lints (#913)

* Start enforcing use_key_in_widget_constructors and file_names lints

* dart format

* analysis fixes

* analysis fixes, pt2

* analysis fixes, part 3

* Revert platform_design (test failure)

* More reverts

* Notate why we aren't enforcing a lint

add_to_app/books/flutter_module_books/lib/api.dart

@@ -94,6 +94,7 @@ abstract class FlutterBookApi {
       if (api == null) {
         channel.setMessageHandler(null);
       } else {
+        // ignore: avoid_types_on_closure_parameters
         channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.FlutterBookApi.displayBookDetails was null.');