fix lateinitialization error in devicelab-runner (#94957)

dev/devicelab/bin/tasks/module_test_ios.dart

@@ -18,7 +18,9 @@ import 'package:path/path.dart' as path;
 /// adding Flutter to an existing iOS app.
 Future<void> main() async {
   await task(() async {
-    late String simulatorDeviceId;
+    // this variable cannot be `late`, as we reference it in the `finally` block
+    // which may execute before this field has been initialized
+    String? simulatorDeviceId;
     section('Create Flutter module project');
 
     final Directory tempDir = Directory.systemTemp.createTempSync('flutter_module_test.');

dev/devicelab/lib/framework/ios.dart

@@ -116,14 +116,14 @@ Future<void> testWithNewIOSSimulator(
 }
 
 /// Shuts down and deletes simulator with deviceId.
-Future<void> removeIOSimulator(String deviceId) async {
+Future<void> removeIOSimulator(String? deviceId) async {
   if (deviceId != null && deviceId != '') {
     await eval(
       'xcrun',
       <String>[
         'simctl',
         'shutdown',
-        deviceId
+        deviceId,
       ],
       canFail: true,
       workingDirectory: flutterDirectory.path,
@@ -133,7 +133,8 @@ Future<void> removeIOSimulator(String deviceId) async {
       <String>[
         'simctl',
         'delete',
-        deviceId],
+        deviceId,
+      ],
       canFail: true,
       workingDirectory: flutterDirectory.path,
     );