[Test] Add @JvmMultifileClass to coroutine helpers files

This is needed to keep compatibility with old format, when all those
  helpers were generated dynamically on test run in one file, so
  you can reference helpers methods from java code just importing
  `helpers.CoroutineUtilKt`

compiler/testData/diagnostics/helpers/coroutines/CoroutineHelpers.kt

@@ -1,3 +1,6 @@
+@file:JvmMultifileClass
+@file:JvmName("CoroutineUtilKt")
+
 package helpers
 
 import kotlin.coroutines.*

compiler/testData/diagnostics/helpers/coroutines/StateMachineChecker.kt

@@ -1,3 +1,6 @@
+@file:JvmMultifileClass
+@file:JvmName("CoroutineUtilKt")
+
 package helpers
 
 import kotlin.coroutines.*

compiler/testData/diagnostics/helpers/coroutines/TailCallOptimizationChecker.kt

@@ -1,3 +1,6 @@
+@file:JvmMultifileClass
+@file:JvmName("CoroutineUtilKt")
+
 package helpers
 
 import kotlin.coroutines.*