Make copy-paste resolve task modal to avoid invalid psi elements

Due to background formatting pasted PSI elements become invalid quite soon and it is not possible to make resolve

#KT-37414 Fixed

idea/src/org/jetbrains/kotlin/idea/codeInsight/KotlinCopyPasteReferenceProcessor.kt

@@ -312,7 +312,7 @@ class KotlinCopyPasteReferenceProcessor : CopyPastePostProcessor<BasicKotlinRefe
         file: KtFile,
         findReferenceProvider: (indicator: ProgressIndicator) -> List<ReferenceToRestoreData>
     ) {
-        val task: Task.Backgroundable = object : Task.Backgroundable(project, "Resolve pasted references", true) {
+        val task = object : Task.Modal(project, "Resolving pasted references ...", true) {
             override fun run(indicator: ProgressIndicator) {
                 assert(!ApplicationManager.getApplication().isWriteAccessAllowed) {
                     "Resolving references on dispatch thread leads to live lock"