Do not use property placeholder in config names

Update ConfigFileApplicationContextInitializer so that the names
property defaults to `${spring.config.name},application`. This allows
application.properties files to be loaded even when property placeholder
expansion is not enabled.

Issue: #54462910

spring-boot/src/main/java/org/springframework/boot/context/initializer/ConfigFileApplicationContextInitializer.java

@@ -89,7 +89,7 @@ public class ConfigFileApplicationContextInitializer implements
 	private String[] searchLocations = new String[] { "classpath:", "file:./",
 			"classpath:config/", "file:./config/" };
 
-	private String names = "${spring.config.name:application}";
+	private String names = "${spring.config.name},application";
 
 	private int order = Integer.MIN_VALUE + 10;