[CQ] stop blocking on FlutterStudioStartupActivity startup (#8093)

See: #8089

Tested on Meerkat, Mac OS.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md

Author: pq

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

@@ -5,35 +5,42 @@
  */
 package io.flutter;
 
+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.project.FlutterProjectCreator;
+import io.flutter.dart.FlutterDartAnalysisServer;
 import io.flutter.settings.FlutterSettings;
 import io.flutter.utils.AddToAppUtils;
 import io.flutter.utils.AndroidUtils;
 import io.flutter.utils.GradleUtils;
 import org.jetbrains.annotations.NotNull;
 
 public class FlutterStudioStartupActivity implements StartupActivity {
-
-  @Override
-  public void runActivity(@NotNull Project project) {
+  private static Void doNonBlockingStartup(@NotNull Project project) {
     if (AndroidUtils.isAndroidProject(project)) {
       GradleUtils.addGradleListeners(project);
     }
     if (!AddToAppUtils.initializeAndDetectFlutter(project)) {
-      return;
+      return null;
     }
-
     // Unset this flag for all projects, mainly to ease the upgrade from 3.0.1 to 3.1.
     // TODO(messick) Delete once 3.0.x has 0 7DA's.
     //FlutterProjectCreator.disableUserConfig(project);
     // Monitor Android dependencies.
-    if (FlutterSettings.getInstance().isSyncingAndroidLibraries() ||
+    FlutterSettings flutterSettings = FlutterSettings.getInstance();
+    if (flutterSettings != null && flutterSettings.isSyncingAndroidLibraries() ||
         System.getProperty("flutter.android.library.sync", null) != null) {
       // TODO(messick): Remove the flag once this sync mechanism is stable.
       AndroidModuleLibraryManager.startWatching(project);
     }
+    return null;
+  }
+
+  @Override
+  public void runActivity(@NotNull Project project) {
+    ReadAction.nonBlocking(() -> doNonBlockingStartup(project)).expireWith(FlutterDartAnalysisServer.getInstance(project))
+      .submit(AppExecutorUtil.getAppExecutorService());
   }
 }