Native: add KotlinThrowable.asError() to the generated Obj-C framework

This method can be useful when overriding a throwing Kotlin method in
Swift or Obj-C. In this case, a user can call asError to wrap Kotlin exception
to (NS)Error and then throw it to Kotlin, which will unwrap it back.

^KT-45127 Fixed

kotlin-native/backend.native/tests/objcexport/throwableAsError.kt

@@ -0,0 +1,38 @@
+package throwableAsError
+
+import kotlin.coroutines.*
+
+class ThrowableAsError : Throwable()
+
+interface ThrowsThrowableAsError {
+    @Throws(Throwable::class)
+    fun throwError()
+}
+
+fun callAndCatchThrowableAsError(throwsThrowableAsError: ThrowsThrowableAsError): ThrowableAsError? {
+    try {
+        throwsThrowableAsError.throwError()
+    } catch (e: ThrowableAsError) {
+        return e
+    }
+
+    return null
+}
+
+interface ThrowsThrowableAsErrorSuspend {
+    suspend fun throwError()
+}
+
+fun callAndCatchThrowableAsErrorSuspend(throwsThrowableAsErrorSuspend: ThrowsThrowableAsErrorSuspend): ThrowableAsError? {
+    var throwable: ThrowableAsError? = null
+    suspend {
+        throwsThrowableAsErrorSuspend.throwError()
+    }.startCoroutine(object : Continuation<Unit> {
+        override val context = EmptyCoroutineContext
+        override fun resumeWith(result: Result<Unit>) {
+            throwable = result.exceptionOrNull() as? ThrowableAsError
+        }
+    })
+
+    return throwable
+}