Upgrade to Kotlin 1.5

* To align with the rest of Spring portfolio, based on Spring Framework 5.3.x generation,
it is better to upgrade to the Kotlin version supported by SF
* Fix  `ClassUtils.isLambda()` to treat `$inlined$` classes as Kotlin lambdas and let
Java DSL to delegate to the `LambdaMessageProcessor` for better expected type handling.
Looks like Kotlin does not carry type info in its lambdas anymore (at least for functions).
* Add `-parameters` to the compiler args for possible method argument names discovery.
Essentially realign with the rest of portfolio
* Fix Kotlin tests for deprecated API

spring-integration-file/src/test/kotlin/org/springframework/integration/kotlin/file/aggregator/KotlinFileAggregatorTests.kt

@@ -42,6 +42,7 @@ import org.springframework.test.context.junit.jupiter.SpringJUnitConfig
 import org.springframework.util.FileCopyUtils
 import java.io.File
 import java.io.FileOutputStream
+import java.util.*
 
 /**
  * @author Artem Bilan
@@ -106,7 +107,7 @@ class KotlinFileAggregatorTests {
 				split(Files.splitter().markers().firstLineAsHeader("firstLine"))
 				channel { executor(taskExecutor) }
 				filter<Any>({ it !is FileMarker }) { discardChannel("aggregatorChannel") }
-				transform(String::toUpperCase)
+				transform(String::uppercase)
 				channel("aggregatorChannel")
 				aggregate(FileAggregator())
 				channel { queue("resultChannel") }