Minor. Use coroutine test helpers for inline/diagnostics tests

It should help with decreasing test data copy-pasting when
testing against release / pre-release coroutines

compiler/testData/codegen/boxInline/suspend/receiver/inlineSuspendOfNoinlineSuspend.kt

@@ -1,8 +1,10 @@
 // FILE: test.kt
 // COMMON_COROUTINES_TEST
 // WITH_RUNTIME
+// WITH_COROUTINES
 
 import COROUTINES_PACKAGE.*
+import helpers.*
 
 // Block is allowed to be called from nested classes/lambdas (as common crossinlines)
 // Are suspend calls possible inside lambda matching to the parameter
@@ -13,17 +15,6 @@ interface SuspendRunnable {
     suspend fun run()
 }
 
-object EmptyContinuation: Continuation<Unit> {
-    override val context: CoroutineContext
-        get() = EmptyCoroutineContext
-
-    override fun resume(value: Unit) {
-    }
-
-    override fun resumeWithException(exception: Throwable) {
-        throw exception
-    }
-}
 
 class Controller {
     var res = "FAIL 1"
@@ -59,6 +50,7 @@ fun builder(controller: Controller, c: suspend Controller.() -> Unit) {
 // COMMON_COROUTINES_TEST
 
 import COROUTINES_PACKAGE.*
+import helpers.*
 
 suspend fun calculate() = "OK"