Native: prohibit calling suspend functions from autoreleasepool {}

If a suspend function is called from `autoreleasepool {}` block, this
might cause the autoreleasepool frame to be removed earlier than
expected. See https://youtrack.jetbrains.com/issue/KT-50786 for more
details.

^KT-50786 Fixed

kotlin-native/backend.native/tests/interop/objc/tests/kt50786.kt

@@ -0,0 +1,34 @@
+package kt50786
+
+import kotlinx.cinterop.*
+import kotlin.coroutines.*
+
+open class EmptyContinuation(override val context: CoroutineContext = EmptyCoroutineContext) : Continuation<Any?> {
+    companion object : EmptyContinuation()
+    override fun resumeWith(result: Result<Any?>) { result.getOrThrow() }
+}
+
+lateinit var continuation: Continuation<Unit>
+
+suspend fun suspendHere(): Unit = suspendCoroutine { cont ->
+    continuation = cont
+}
+
+
+fun startCoroutine(block: suspend () -> Unit) {
+    block.startCoroutine(EmptyContinuation)
+}
+
+@kotlin.test.Test
+fun testSafeSuspensionIsAllowedInAutoreleasepool() {
+    // This test checks that the compiler doesn't prohibit calling suspend functions from `autoreleasepool {}`
+    // if this call is not actually in the block, but in the local declaration inside it.
+    // See https://youtrack.jetbrains.com/issue/KT-50786 for more details.
+    autoreleasepool {
+        startCoroutine {
+            suspendHere()
+        }
+    }
+
+    continuation.resume(Unit)
+}