feat: migrate fuchsia/application_package.dart to null-safe (#88095)

packages/flutter_tools/lib/src/fuchsia/application_package.dart

@@ -2,10 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
-import 'package:meta/meta.dart';
-
 import '../application_package.dart';
 import '../base/file_system.dart';
 import '../build_info.dart';
@@ -13,10 +9,10 @@ import '../globals_null_migrated.dart' as globals;
 import '../project.dart';
 
 abstract class FuchsiaApp extends ApplicationPackage {
-  FuchsiaApp({@required String projectBundleId}) : super(id: projectBundleId);
+  FuchsiaApp({required String projectBundleId}) : super(id: projectBundleId);
 
   /// Creates a new [FuchsiaApp] from a fuchsia sub project.
-  factory FuchsiaApp.fromFuchsiaProject(FuchsiaProject project) {
+  static FuchsiaApp? fromFuchsiaProject(FuchsiaProject project) {
     if (!project.existsSync()) {
       // If the project doesn't exist at all the current hint to run flutter
       // create is accurate.
@@ -30,7 +26,7 @@ abstract class FuchsiaApp extends ApplicationPackage {
   /// Creates a new [FuchsiaApp] from an existing .far archive.
   ///
   /// [applicationBinary] is the path to the .far archive.
-  factory FuchsiaApp.fromPrebuiltApp(FileSystemEntity applicationBinary) {
+  static FuchsiaApp? fromPrebuiltApp(FileSystemEntity applicationBinary) {
     final FileSystemEntityType entityType = globals.fs.typeSync(applicationBinary.path);
     if (entityType != FileSystemEntityType.file) {
       globals.printError('File "${applicationBinary.path}" does not exist or is not a .far file. Use far archive.');
@@ -50,7 +46,7 @@ abstract class FuchsiaApp extends ApplicationPackage {
 
 class PrebuiltFuchsiaApp extends FuchsiaApp {
   PrebuiltFuchsiaApp({
-    @required String farArchive,
+    required String farArchive,
   }) : _farArchive = farArchive,
        // TODO(zra): Extract the archive and extract the id from meta/package.
        super(projectBundleId: farArchive);
@@ -65,7 +61,7 @@ class PrebuiltFuchsiaApp extends FuchsiaApp {
 }
 
 class BuildableFuchsiaApp extends FuchsiaApp {
-  BuildableFuchsiaApp({this.project}) :
+  BuildableFuchsiaApp({required this.project}) :
       super(projectBundleId: project.project.manifest.appName);
 
   final FuchsiaProject project;