Make Kotlin functions accessible in CoroutinesUtils

In order to allow using private classes like in Java
for example.

Closes gh-23840

spring-core/src/main/java/org/springframework/core/CoroutinesUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +25,7 @@ import kotlin.jvm.JvmClassMappingKt;
 import kotlin.reflect.KClassifier;
 import kotlin.reflect.KFunction;
 import kotlin.reflect.full.KCallables;
+import kotlin.reflect.jvm.KCallablesJvm;
 import kotlin.reflect.jvm.ReflectJvmMapping;
 import kotlinx.coroutines.BuildersKt;
 import kotlinx.coroutines.CoroutineStart;
@@ -70,6 +71,9 @@ public abstract class CoroutinesUtils {
 	 */
 	public static Publisher<?> invokeSuspendingFunction(Method method, Object target, Object... args) {
 		KFunction<?> function = Objects.requireNonNull(ReflectJvmMapping.getKotlinFunction(method));
+		if (method.isAccessible() && !KCallablesJvm.isAccessible(function)) {
+			KCallablesJvm.setAccessible(function, true);
+		}
 		KClassifier classifier = function.getReturnType().getClassifier();
 		Mono<Object> mono = MonoKt.mono(Dispatchers.getUnconfined(), (scope, continuation) ->
 					KCallables.callSuspend(function, getSuspendedFunctionArgs(target, args), continuation))