[Enhancement](group commit) optimize some group commit code (#31392)

This PR optimizes some of the logic related to group commit:
1. Improved the error handling when there is insufficient WAL space during import.
2. Accounted for cases where the content length is negative during import.
3. Added missing error log printing in `group_commit_mgr.cpp`.

be/src/runtime/group_commit_mgr.cpp

@@ -276,6 +276,9 @@ Status GroupCommitTable::_create_group_commit_load(
                 client->streamLoadPut(result, request);
             },
             10000L);
+    if (!st.ok()) {
+        LOG(WARNING) << "create group commit load rpc error, st=" << st.to_string();
+    }
     RETURN_IF_ERROR(st);
     st = Status::create<false>(result.status);
     if (!st.ok()) {