Demote the "test dir mapping" log message to debug

This log message of the gradle application plugin seems to be
unnecessary and confusing to the ordinary plugin user (i.e.
a developer building a Quarkus application with Gradle).

(cherry picked from commit cc2048b)

devtools/gradle/gradle-application-plugin/src/main/java/io/quarkus/gradle/extension/QuarkusPluginExtension.java

@@ -77,7 +77,7 @@ public void beforeTest(Test task) {
                             project.relativePath(outputDirectoryAsFile)))
                     .collect(Collectors.joining(","));
             task.environment(BootstrapConstants.TEST_TO_MAIN_MAPPINGS, fileList);
-            project.getLogger().lifecycle("test dir mapping - {}", fileList);
+            project.getLogger().debug("test dir mapping - {}", fileList);
 
             final String nativeRunner = task.getProject().getBuildDir().toPath().resolve(finalName() + "-runner")
                     .toAbsolutePath()