Log Docker output to aid debugging

Add an SLF4J logger so that we can see real time output of the
Docker container.

See gh-29370

spring-boot-tests/spring-boot-integration-tests/spring-boot-launch-script-tests/src/intTest/java/org/springframework/boot/launchscript/AbstractLaunchScriptIntegrationTests.java

@@ -23,7 +23,9 @@ import java.util.List;
 import java.util.function.Predicate;
 
 import org.assertj.core.api.Condition;
+import org.slf4j.LoggerFactory;
 import org.testcontainers.containers.GenericContainer;
+import org.testcontainers.containers.output.Slf4jLogConsumer;
 import org.testcontainers.containers.output.ToStringConsumer;
 import org.testcontainers.containers.startupcheck.OneShotStartupCheckStrategy;
 import org.testcontainers.images.builder.ImageFromDockerfile;
@@ -85,6 +87,7 @@ abstract class AbstractLaunchScriptIntegrationTests {
 		try (LaunchScriptTestContainer container = new LaunchScriptTestContainer(os, version, this.scriptsDir,
 				script)) {
 			container.withLogConsumer(consumer);
+			container.withLogConsumer(new Slf4jLogConsumer(LoggerFactory.getLogger("docker")));
 			container.start();
 			while (container.isRunning()) {
 				Thread.sleep(100);

src/checkstyle/checkstyle-suppressions.xml

@@ -52,4 +52,5 @@
 	<suppress files="StringSequence" checks="SpringMethodVisibility" message="isEmpty"/>
 	<suppress files="ValidatorPropertiesWithDefaultValues\.java" checks="SpringMethodVisibility" />
 	<suppress files="DevToolsR2dbcAutoConfigurationTests" checks="HideUtilityClassConstructor" />
+	<suppress files="AbstractLaunchScriptIntegrationTests" checks="IllegalImport" />
 </suppressions>