Function validate_things

Peform validation using the Things (test) split

(model,
                    padding_factor=8,
                    with_speed_metric=False,
                    max_val_flow=400,
                    val_things_clean_only=True,
                    attn_type='swin',
                    attn_splits_list=False,
                    corr_radius_list=False,
                    prop_radius_list=False,
                    num_reg_refine=1,
                    )