Add metadata for logging.level

Closes gh-1992

spring-boot/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -16,6 +16,12 @@
     "description": "The name of the log file.",
     "sourceType": "org.springframework.boot.logging.LoggingApplicationListener"
   },
+  {
+    "name": "logging.level",
+    "type": "java.util.Map<java.lang.String,java.lang.Object>",
+    "description": "The log levels. Use 'root' for the root logger.",
+    "sourceType": "org.springframework.boot.logging.LoggingApplicationListener"
+  },
   {
     "name": "logging.path",
     "type": "java.lang.String",