[CQ] migrate FlutterStudioStartupActivity to a project activity (#8211)

The model for this change was set with
#8200 and ties up our
migration off of the deprecated `StartupActivity` in favor of project
activities, leveraging IntelliJ's embrace of Kotlin coroutines for
improved startup performance.

Fixes: #8100



---

- [x] I’ve reviewed the contributor guide and applied the relevant
portions to this PR.

<details>
  <summary>Contribution guidelines:</summary><br>

- See our [contributor
guide]([https://github.com/dart-lang/sdk/blob/main/CONTRIBUTING.md](https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview)
for general expectations for PRs.
- Larger or significant changes should be discussed in an issue before
creating a PR.
- Dart contributions to our repos should follow the [Dart style
guide](https://dart.dev/guides/language/effective-dart) and use `dart
format`.
- Java and Kotlin contributions should strive to follow Java and Kotlin
best practices
([discussion](#8098)).
</details>

Author: pq

flutter-studio/src/io/flutter/FlutterStudioStartupActivity.java

@@ -7,7 +7,6 @@
 
 import com.intellij.openapi.application.ReadAction;
 import com.intellij.openapi.project.Project;
-import com.intellij.openapi.startup.StartupActivity;
 import com.intellij.util.concurrency.AppExecutorUtil;
 import io.flutter.android.AndroidModuleLibraryManager;
 import io.flutter.dart.FlutterDartAnalysisServer;
@@ -17,7 +16,7 @@
 import io.flutter.utils.GradleUtils;
 import org.jetbrains.annotations.NotNull;
 
-public class FlutterStudioStartupActivity implements StartupActivity {
+public class FlutterStudioStartupActivity extends FlutterProjectActivity {
   private static Void doNonBlockingStartup(@NotNull Project project) {
     if (AndroidUtils.isAndroidProject(project)) {
       GradleUtils.addGradleListeners(project);
@@ -39,7 +38,7 @@ private static Void doNonBlockingStartup(@NotNull Project project) {
   }
 
   @Override
-  public void runActivity(@NotNull Project project) {
+  public void executeProjectStartup(@NotNull Project project) {
     ReadAction.nonBlocking(() -> doNonBlockingStartup(project)).expireWith(FlutterDartAnalysisServer.getInstance(project))
       .submit(AppExecutorUtil.getAppExecutorService());
   }