[perf] stop static initialization in line marker extension (#8114)

![image](https://github.com/user-attachments/assets/bffce434-6527-4501-95d7-129541d8b4b7)

From the inspection description:

> Static initialization is performed once the class is loaded, which may
cause excessive classloading or early initialization of heavy resources.
Since extension point implementations are supposed to be cheap to
create, they must not have static initializers.

---

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portions to this PR.

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Author: pq

flutter-idea/src/io/flutter/editor/FlutterIconLineMarkerProvider.java

@@ -55,8 +55,16 @@ public class FlutterIconLineMarkerProvider extends LineMarkerProviderDescriptor
   private static final String CupertinoRelativeAssetPath = "/assets/CupertinoIcons.ttf";
   private static final String CupertinoRelativeIconsPath = "/packages/flutter/lib/src/cupertino/icons.dart";
 
-  static {
-    initialize();
+  private static boolean instantiated = false;
+
+  FlutterIconLineMarkerProvider() {
+    // Extension point implementations can't use static initializers so we keep track of the
+    // first instantiation to make sure #initialize is called to set up initial state. (Note that this state
+    // may get reset with a subsequent explicit call to #initialize.)
+    if (!instantiated) {
+      initialize();
+    }
+    instantiated = true;
   }
 
   public static void initialize() {