message: bpls: Simplify variable and attribute count lookup
  Use `GetVariables` and `GetAttributes` directly to avoid constructing a
  whole variable or attribute map just to get its size.
diff: @@ -1474,13 +1474,9 @@ int doList(const char *path)
  // ntsteps = fp->tidx_stop - fp->tidx_start + 1;
  if (verbose)
  {
  - const std::map<std::string, Params> &variablesInfo =
  - io.GetAvailableVariables();
  - const std::map<std::string, Params> &attributesInfo =
  - io.GetAvailableAttributes();
  printf("File info:\n");
  - printf(" of variables: %zu\n", variablesInfo.size());
  - printf(" of attributes: %zu\n", attributesInfo.size());
  + printf(" of variables: %zu\n", io.GetVariables().size());
  + printf(" of attributes: %zu\n", io.GetAttributes().size());
  // printf(" of meshes: %d\n", fp->nmeshes);
  // print_file_size(fp->file_size);
  // printf(" bp version: %d\n", fp->version);
  