Move Kotlin value class unboxing to InvocableHandlerMethod

Before this commit, in Spring Framework 6.2, Kotlin value class
unboxing was done at CoroutinesUtils level, which is a good fit
for InvocableHandlerMethod use case, but not for other ones like
AopUtils.

This commit moves such unboxing to InvocableHandlerMethod in
order to keep the HTTP response body support while fixing other
regressions.

Closes gh-33943

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

@@ -44,7 +44,6 @@ import kotlinx.coroutines.reactor.ReactorFlowKt;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
-import reactor.core.publisher.SynchronousSink;
 
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -109,7 +108,7 @@ public abstract class CoroutinesUtils {
 	 * @throws IllegalArgumentException if {@code method} is not a suspending function
 	 * @since 6.0
 	 */
-	@SuppressWarnings({"deprecation", "DataFlowIssue", "NullAway"})
+	@SuppressWarnings({"DataFlowIssue", "NullAway"})
 	public static Publisher<?> invokeSuspendingFunction(
 			CoroutineContext context, Method method, @Nullable Object target, @Nullable Object... args) {
 
@@ -146,7 +145,7 @@ public abstract class CoroutinesUtils {
 					}
 					return KCallables.callSuspendBy(function, argMap, continuation);
 				})
-				.handle(CoroutinesUtils::handleResult)
+				.filter(result -> result != Unit.INSTANCE)
 				.onErrorMap(InvocationTargetException.class, InvocationTargetException::getTargetException);
 
 		KType returnType = function.getReturnType();
@@ -166,22 +165,4 @@ public abstract class CoroutinesUtils {
 		return ReactorFlowKt.asFlux(((Flow<?>) flow));
 	}
 
-	private static void handleResult(Object result, SynchronousSink<Object> sink) {
-		if (result == Unit.INSTANCE) {
-			sink.complete();
-		}
-		else if (KotlinDetector.isInlineClass(result.getClass())) {
-			try {
-				sink.next(result.getClass().getDeclaredMethod("unbox-impl").invoke(result));
-				sink.complete();
-			}
-			catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException ex) {
-				sink.error(ex);
-			}
-		}
-		else {
-			sink.next(result);
-			sink.complete();
-		}
-	}
 }