Issue: LocalDatasetModuleFactoryWithoutScript extracts invalid builder name

## Describe the bug
Trying to load a local dataset raises an error indicating that the config builder has to have a name.
No error should be reported, since the call is completly valid.

## Steps to reproduce the bug
```python
load_dataset("./data/some-dataset/", name="some-name")
```

## Expected results
The dataset should be loaded.

## Actual results
```
Traceback (most recent call last):
  File "train_lquad.py", line 19, in <module>
    load(tokenize_target_function, tokenize_target_function, {}, tokenizer)
  File "train_lquad.py", line 14, in load
    dataset = load_dataset("./data/lquad/", name="lquad")
  File "/net/pr2/scratch/people/plgapohl/python-3.8.6/lib/python3.8/site-packages/datasets/load.py", line 1708, in load_dataset                                                                           
    builder_instance = load_dataset_builder(
  File "/net/pr2/scratch/people/plgapohl/python-3.8.6/lib/python3.8/site-packages/datasets/load.py", line 1560, in load_dataset_builder                                                                   
    builder_instance: DatasetBuilder = builder_cls(
  File "/net/pr2/scratch/people/plgapohl/python-3.8.6/lib/python3.8/site-packages/datasets/builder.py", line 269, in __init__                                                                             
    self.config, self.config_id = self._create_builder_config(
  File "/net/pr2/scratch/people/plgapohl/python-3.8.6/lib/python3.8/site-packages/datasets/builder.py", line 403, in _create_builder_config                                                               
    raise ValueError(f"BuilderConfig must have a name, got {builder_config.name}")
ValueError: BuilderConfig must have a name, got
```

## Environment info
- `datasets` version: 2.2.2
- Platform: Linux-4.18.0-348.20.1.el8_5.x86_64-x86_64-with-glibc2.2.5
- Python version: 3.8.6
- PyArrow version: 8.0.0
- Pandas version: 1.4.2

The error is probably in line 795 in load.py:

```
 builder_kwargs = {                        
     "hash": hash,
     "data_files": data_files,
     "name": os.path.basename(self.path),
     "base_path": self.path,
     **builder_kwargs,
 }
```

`os.path.basename` for a directory returns an empty string, rather than the name of the directory.


Comments:
Ok, so
```
os.path.basename("/home/user/")
```
gives `''` while 
```
os.path.basename("/home/user")
```
gives `user`. 
The code should check if the last char is a slash.


The fix is:
```
"name": os.path.basename(self.path[:-1] if self.path[-1] == "/" else self.path)
```

I came through the same issue , just removing the last slash in the dataset path fixed it for me, may be this repo moderators could accept this as an accepted answer atleast if this could not be integrated

> The fix is:
> 
> ```
> "name": os.path.basename(self.path[:-1] if self.path[-1] == "/" else self.path)
> ```

@apohllo consider making a pull request on this 

Thanks for the amazing contributions from huggingface people !!


@apohllo Would you be interested in submitting a PR with the fix?

@mariosasko here we go:

https://github.com/huggingface/datasets/pull/4967

TBH I haven't tested it yet, but should work, since this is a basic change.