Optimize KotlinScriptDependenciesClassFinder

Do not call processDirectories for all package prefixes checking inner classes

^KT-39796 Fixed

idea/testData/script/definition/highlighting/nestedClass/lib/lib/JavaInterface.java

@@ -0,0 +1,13 @@
+package lib;
+
+public interface JavaInterface {
+    public interface F {
+        public interface I {
+
+        }
+    }
+
+    public class G {
+
+    }
+}

idea/testData/script/definition/highlighting/nestedClass/lib/lib/KotlinInterface.kt

@@ -0,0 +1,9 @@
+package lib
+
+interface KotlinInterface {
+    interface F {
+        interface I
+    }
+
+    class G
+}