Test that Kotlin synthetic classes work in SpEL

Related to spring-projects/spring-framework#23812

* Modify `FunctionsTests.kt` test to be sure that fall back to SpEL
invocation in case of Kotlin lambda works as expected.
This is like an additional test to the fix in Spring Framework

build.gradle

@@ -93,7 +93,7 @@ ext {
 	springDataVersion = 'Moore-SR1'
 	springSecurityVersion = '5.2.1.RELEASE'
 	springRetryVersion = '1.2.4.RELEASE'
-	springVersion = project.hasProperty('springVersion') ? project.springVersion : '5.2.1.RELEASE'
+	springVersion = project.hasProperty('springVersion') ? project.springVersion : '5.2.2.BUILD-SNAPSHOT'
 	springWsVersion = '3.0.8.RELEASE'
 	tomcatVersion = "9.0.27"
 	xstreamVersion = '1.4.11.1'

spring-integration-core/src/test/kotlin/org/springframework/integration/function/FunctionsTests.kt

@@ -167,7 +167,8 @@ class FunctionsTests {
 
 		@Bean
 		fun flowFromSupplier() =
-				IntegrationFlows.from<String>({ "bar" }) { e -> e.poller { p -> p.fixedDelay(10).maxMessagesPerPoll(1) } }
+				IntegrationFlows.from<String>({ "" }) { e -> e.poller { p -> p.fixedDelay(10).maxMessagesPerPoll(1) } }
+						.transform<String, String> { "blank" }
 						.channel { c -> c.queue("fromSupplierQueue") }
 						.get()