Add Spring Kafka test utilities to Kafka test starter

Closes gh-47793

smoke-test/spring-boot-smoke-test-kafka/build.gradle

@@ -44,7 +44,6 @@ dependencies {
 
 	testImplementation(project(":starter:spring-boot-starter-kafka-test"))
 	testImplementation("org.awaitility:awaitility")
-	testImplementation("org.springframework.kafka:spring-kafka-test")
 }
 
 tasks.named("compileTestJava") {

starter/spring-boot-starter-kafka-test/build.gradle

@@ -23,4 +23,14 @@ description = "Starter for testing Apache Kafka"
 dependencies {
 	api(project(":starter:spring-boot-starter-kafka"))
 	api(project(":starter:spring-boot-starter-test"))
+	api("org.springframework.kafka:spring-kafka-test") {
+		exclude group: "org.apache.logging.log4j", module: "log4j-slf4j-impl"
+	}
+}
+
+checkRuntimeClasspathForConflicts {
+	ignore { name -> name == "NOTICE" ||
+				name.equals("kafka/kafka-version.properties") ||
+				name.equals("log4j2.yaml")
+	}
 }