Add ContinuationAdapter to coroutine tests helpers

It allows having the same Continuation implementations for different
API versions

compiler/testData/codegen/boxInline/suspend/inlineUsedAsNoinline/inlineOnly.kt

@@ -1,6 +1,7 @@
 // IGNORE_BACKEND: JVM_IR
 // FILE: inlined.kt
 // WITH_RUNTIME
+// WITH_COROUTINES
 // NO_CHECK_LAMBDA_INLINING
 
 import kotlin.coroutines.experimental.*
@@ -33,7 +34,7 @@ import kotlin.coroutines.experimental.*
 import kotlin.coroutines.experimental.intrinsics.*
 
 fun builder(c: suspend () -> Unit) {
-    val continuation = object: Continuation<Unit> {
+    val continuation = object: helpers.ContinuationAdapter<Unit>() {
         override val context: CoroutineContext
             get() = EmptyCoroutineContext
 
@@ -69,4 +70,4 @@ fun box(): String {
     proceed()
     if (!finished) return "resume on root continuation is not called"
     return result
-}
+}

compiler/testData/codegen/boxInline/suspend/inlineUsedAsNoinline/simpleNamed.kt

@@ -1,6 +1,7 @@
 // IGNORE_BACKEND: JVM_IR
 // FILE: inlined.kt
 // WITH_RUNTIME
+// WITH_COROUTINES
 // NO_CHECK_LAMBDA_INLINING
 
 import kotlin.coroutines.experimental.*
@@ -31,7 +32,7 @@ import kotlin.coroutines.experimental.*
 import kotlin.coroutines.experimental.intrinsics.*
 
 fun builder(c: suspend () -> Unit) {
-    val continuation = object: Continuation<Unit> {
+    val continuation = object: helpers.ContinuationAdapter<Unit>() {
         override val context: CoroutineContext
             get() = EmptyCoroutineContext
 
@@ -67,4 +68,4 @@ fun box(): String {
     proceed()
     if (!finished) return "resume on root continuation is not called"
     return result
-}
+}