Make replyContainer as bean in Kafka tests

It looks like `replyContainer()` is not registered as a bean,
so its lifecycle is somehow out of application context control

* Mark `replyContainer()` method as a `@Bean` in the `KafkaDslTests` and `KafkaDslKotlinTests`
to see if this fixes flaky state of the test suite
* Upgrade to Kotlin `1.7.20` and fix `KafkaDslKotlinTests` according to its requirements

build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlinVersion = '1.7.10'
+    ext.kotlinVersion = '1.7.20'
     ext.isCI = System.getenv('GITHUB_ACTION') || System.getenv('bamboo_buildKey')
     repositories {
         mavenCentral()