[ds-inference] checkpoint loading => tqdm (#2107)
* [ds-inference] checkpoint loading => tqdm
solve 2 issues:
- less noise using tqdm progress bar
- more informative - tell users how much to wait and how many shards to load
New way:
```
Loading 72 checkpoints: 12%|█▎ | 9/72 [01:12<08:39, 8.25s/it]
```
* write only from one process
* style