message: FAPL: add tests for core_filebacked()
  (rustfmt)
diff: @@ -204,6 +204,16 @@ fn test_fapl_driver_core() -> h5::Result<()> {
  #[cfg(hdf5_1_8_13)]
  assert_eq!(d.write_tracking, 456);
  + b.core_filebacked(false);
  + let d = check_matches!(b.finish()?.get_driver()?, d, FileDriver::Core(d));
  + assert_eq!(d.increment, CoreDriver::default().increment);
  + assert_eq!(d.filebacked, false);
  +
  + b.core_filebacked(true);
  + let d = check_matches!(b.finish()?.get_driver()?, d, FileDriver::Core(d));
  + assert_eq!(d.increment, CoreDriver::default().increment);
  + assert_eq!(d.filebacked, true);
  +
  Ok(())
  }
  