gradle.kts: add clearCaches method for testing

idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/ScriptConfigurationManager.kt

@@ -160,5 +160,10 @@ interface ScriptConfigurationManager {
         fun updateScriptDependenciesSynchronously(file: PsiFile, project: Project) {
             (getInstance(project) as AbstractScriptConfigurationManager).updateScriptDependenciesSynchronously(file)
         }
+
+        @TestOnly
+        fun clearCaches(project: Project) {
+            (getInstance(project) as AbstractScriptConfigurationManager).clearCaches()
+        }
     }
 }

idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/configuration/AbstractScriptConfigurationManager.kt

@@ -222,6 +222,7 @@ internal abstract class AbstractScriptConfigurationManager(
     override fun clearConfigurationCachesAndRehighlight() {
         ScriptDependenciesModificationTracker.getInstance(project).incModificationCount()
 
+        // todo: cache.clear()
         clearClassRootsCaches()
 
         if (project.isOpen) {
@@ -230,6 +231,11 @@ internal abstract class AbstractScriptConfigurationManager(
         }
     }
 
+    @TestOnly
+    internal fun clearCaches() {
+        cache.clear()
+    }
+
     private fun updateHighlighting(files: List<VirtualFile>) {
         if (files.isEmpty()) return