Add EmptyLineSeparator Checkstyle rule

* Support "blank lines around" via `spring-framework.xml` IDEA config
* Fix all the Checkstyle violations

spring-integration-test-support/src/main/java/org/springframework/integration/test/rule/Log4j2LevelAdjuster.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2018-2022 the original author or authors.
+ * Copyright 2018-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -89,6 +89,7 @@ public final class Log4j2LevelAdjuster implements MethodRule {
 			}
 
 		}
+
 		return new AdjustingStatement();
 	}
 

spring-integration-test-support/src/main/java/org/springframework/integration/test/support/RequestResponseScenario.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2021 the original author or authors.
+ * Copyright 2011-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -131,7 +131,6 @@ public class RequestResponseScenario {
 		return this;
 	}
 
-
 	/**
 	 * Set the request message (as an alternative to setPayload())
 	 * @param message The message.

spring-integration-test-support/src/main/java/org/springframework/integration/test/util/OnlyOnceTrigger.java

@@ -47,7 +47,6 @@ public class OnlyOnceTrigger implements Trigger {
 
 	private volatile CountDownLatch latch = new CountDownLatch(1);
 
-
 	public OnlyOnceTrigger() {
 		this.executionTime = Instant.now();
 	}

spring-integration-test-support/src/main/java/org/springframework/integration/test/util/TestUtils.java

@@ -156,7 +156,6 @@ public abstract class TestUtils {
 		applicationContext.registerBean(beanName, (Class<Object>) bean.getClass(), () -> bean);
 	}
 
-
 	/**
 	 * A {@link GenericApplicationContext} extension with some support methods
 	 * to register Spring Integration beans in the application context at runtime.