Print stack trace as string if the processing of config metadata fails

config/metadata-processor/src/main/java/io/helidon/config/metadata/processor/ConfigMetadataHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2023 Oracle and/or its affiliates.
+ * Copyright (c) 2021, 2024 Oracle and/or its affiliates.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.io.StringWriter;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.LinkedHashSet;
@@ -92,9 +93,11 @@ boolean process(RoundEnvironment roundEnv) {
         try {
             return doProcess(roundEnv);
         } catch (Exception e) {
+            StringWriter sw = new StringWriter();
+            PrintWriter pw = new PrintWriter(sw);
+            e.printStackTrace(pw);
             messager.printMessage(Diagnostic.Kind.ERROR, "Failed to process config metadata annotation processor. "
-                    + toMessage(e));
-            e.printStackTrace();
+                    + sw);
             return false;
         }
     }