Make CHECKCAST Object not break tail-call optimization

Since CHECKCAST Object does nothing for return value of suspend
function - the function returns references only, this is safe.
 #KT-49157 Fixed

compiler/testData/codegen/box/coroutines/tailCallOptimizations/deferredAwaitSuspendImpl.kt

@@ -0,0 +1,32 @@
+// TARGET_BACKEND: JVM
+// FULL_JDK
+// WITH_RUNTIME
+// WITH_COROUTINES
+// CHECK_TAIL_CALL_OPTIMIZATION
+import helpers.*
+import kotlin.coroutines.*
+import kotlin.coroutines.intrinsics.*
+
+suspend fun awaitInternal(): Any? = TailCallOptimizationChecker.saveStackTrace()
+
+interface Deferred<out T> {
+    suspend fun await(): T
+}
+
+open class DeferredCoroutine<T> : Deferred<T> {
+    override suspend fun await(): T = awaitInternal() as T
+}
+
+fun builder(c: suspend () -> Unit) {
+    c.startCoroutine(Continuation(EmptyCoroutineContext) {
+        it.getOrThrow()
+    })
+}
+
+fun box(): String {
+    builder {
+        DeferredCoroutine<String>().await()
+    }
+    TailCallOptimizationChecker.checkNoStateMachineIn("await\$suspendImpl")
+    return "OK"
+}