Log more information when mappings fail on index creation (#61577)

Errors from bad mappings at index creation are currently logged at DEBUG level, which
can make it difficult to work out what's going on if the index is being auto-created. This
commit ups the log level to INFO for auto-created indices, and includes some more
information in the log message.

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataCreateIndexService.java

@@ -392,7 +392,8 @@ public class MetadataCreateIndexService {
             try {
                 updateIndexMappingsAndBuildSortOrder(indexService, request, mappings, sourceMetadata);
             } catch (Exception e) {
-                logger.debug("failed on parsing mappings on index creation [{}]", request.index());
+                logger.log(silent ? Level.DEBUG : Level.INFO,
+                    "failed on parsing mappings on index creation [{}]", request.index(), e);
                 throw e;
             }