GH-8705 Expose errorOnTimeout on MessagingGateway

Fixes https://github.com/spring-projects/spring-integration/issues/8705

an internal `MethodInvocationGateway` is a `MessagingGatewaySupport`
extension with all the logic available there.
One of the option introduced in `5.2.2` to be able to throw a `MessageTimeoutException`
instead of returning `null` when no reply received in time from downstream flow

* Expose an `errorOnTimeout` on the `@MessagingGateway` and `GatewayEndpointSpec`
* Propagate this option from a `GatewayProxyFactoryBean` down to its internal
`MethodInvocationGateway` implementation
* Modify couple tests to react for `errorOnTimeout` set to `true`
* Document the feature

Fix language in Docs

Co-authored-by: Gary Russell <grussell@vmware.com>

src/reference/antora/modules/ROOT/pages/gateway.adoc

@@ -794,6 +794,8 @@ If a component downstream is still running (perhaps because of an infinite loop
 However, if the timeout has been reached before the actual reply was produced, it could result in a 'null' return from the gateway method.
 You should understand that the reply message (if produced) is sent to a reply channel after the gateway method invocation might have returned, so you must be aware of that and design your flow with it in mind.
 
+Also see the `errorOnTimeout` property to throw a `MessageTimeoutException` instead of returning `null`, when a timeout occurs.
+
 [[downstream-component-returns-null-]]
 === Downstream Component Returns 'null'
 
@@ -838,4 +840,8 @@ At that time, the calling thread starts waiting for the reply.
 If the flow was completely synchronous, the reply is immediately available.
 For asynchronous flows, the thread waits for up to this time.
 
+Starting with version 6.2, the `errorOnTimeout` property of the internal `MethodInvocationGateway` extension of the `MessagingGatewaySupport` is exposed on the `@MessagingGateway` and `GatewayEndpointSpec`.
+This option has exactly the same meaning as for any inbound gateway explained in the end of xref:endpoint-summary.adoc#endpoint-summary[Endpoint Summary] chapter.
+In other words, setting this option to `true`, would lead to the `MessageTimeoutException` being thrown from a send-and-receive gateway operation instead of returning `null` when the receive timeout is exhausted.
+
 See xref:dsl/integration-flow-as-gateway.adoc[`IntegrationFlow` as Gateway] in the Java DSL chapter for options to define gateways through `IntegrationFlow`.

src/reference/antora/modules/ROOT/pages/whats-new.adoc

@@ -36,6 +36,8 @@ See, for example, `transformWith()`, `splitWith()` in xref:dsl.adoc#java-dsl[ Ja
 - A new `spring.integration.endpoints.defaultTimeout` global property has been introduced to override the default 30 seconds timeout for all the endpoints in the application.
 See xref:configuration/global-properties.adoc[Global Properties] for more information.
 
+- The `@MessagingGateway` and `GatewayEndpointSpec` provided by the Java DSL now expose the `errorOnTimeout` property of the internal `MethodInvocationGateway` extension of the `MessagingGatewaySupport`.
+See xref:gateway.adoc#gateway-no-response[ Gateway Behavior When No response Arrives] for more information.
 [[x6.2-websockets]]
 === WebSockets Changes