[improvement](schemachange) add schema change log (#31145) (#31203)

fe/fe-core/src/main/java/org/apache/doris/alter/AlterJobV2.java

@@ -222,6 +222,7 @@ public abstract class AlterJobV2 implements Writable {
                     break;
             }
         } catch (AlterCancelException e) {
+            LOG.error("failed to run alter job {}", jobId, e);
             cancelImpl(e.getMessage());
         }
     }