FORCE_REDOWNLOAD does not work
Hi ! Thanks for reporting. The error seems to happen only if you use compressed files.

The second dataset is prepared in another dataset cache directory than the first - which is normal, since the source file is different. However, it doesn't uncompress the new data file because it finds the old uncompressed data in the extraction cache directory.

If we fix the extraction cache mechanism to uncompress a local file if it changed then it should fix the issue.
Currently the extraction cache mechanism only takes into account the path of the compressed file, which is an issue.
## Describe the bug
With GenerateMode.FORCE_REDOWNLOAD, the documentation says 
    +------------------------------------+-----------+---------+
    |                                    | Downloads | Dataset |
    +====================================+===========+=========+
    | `REUSE_DATASET_IF_EXISTS` (default)| Reuse     | Reuse   |
    +------------------------------------+-----------+---------+
    | `REUSE_CACHE_IF_EXISTS`            | Reuse     | Fresh   |
    +------------------------------------+-----------+---------+
    | `FORCE_REDOWNLOAD`                 | Fresh     | Fresh   |
    +------------------------------------+-----------+---------+

However, the old dataset is loaded even when FORCE_REDOWNLOAD is chosen.

## Steps to reproduce the bug
```python

import pandas as pd
from datasets import load_dataset, GenerateMode
pd.DataFrame(range(5), columns=['numbers']).to_csv('/tmp/test.tsv.gz', index=False)
ee = load_dataset('csv', data_files=['/tmp/test.tsv.gz'], delimiter='\t', split='train', download_mode=GenerateMode.FORCE_REDOWNLOAD)
print(ee)
pd.DataFrame(range(10), columns=['numerals']).to_csv('/tmp/test.tsv.gz', index=False)
ee = load_dataset('csv', data_files=['/tmp/test.tsv.gz'], delimiter='\t', split='train', download_mode=GenerateMode.FORCE_REDOWNLOAD)
print(ee)

```

## Expected results
Dataset({
    features: ['numbers'],
    num_rows: 5
})
Dataset({
    features: ['numerals'],
    num_rows: 10
})

## Actual results
Dataset({
    features: ['numbers'],
    num_rows: 5
})
Dataset({
    features: ['numbers'],
    num_rows: 5
})


## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.8.0
- Platform: Linux-4.14.181-108.257.amzn1.x86_64-x86_64-with-glibc2.10
- Python version: 3.7.10
- PyArrow version: 3.0.0

FORCE_REDOWNLOAD does not work 
 ## Describe the bug
With GenerateMode.FORCE_REDOWNLOAD, the documentation says 
    +------------------------------------+-----------+---------+
    |                                    | Downloads | Dataset |
    +====================================+===========+=========+
    | `REUSE_DATASET_IF_EXISTS` (default)| Reuse     | Reuse   |
    +------------------------------------+-----------+---------+
    | `REUSE_CACHE_IF_EXISTS`            | Reuse     | Fresh   |
    +------------------------------------+-----------+---------+
    | `FORCE_REDOWNLOAD`                 | Fresh     | Fresh   |
    +------------------------------------+-----------+---------+

However, the old dataset is loaded even when FORCE_REDOWNLOAD is chosen.

## Steps to reproduce the bug
```python

import pandas as pd
from datasets import load_dataset, GenerateMode
pd.DataFrame(range(5), columns=['numbers']).to_csv('/tmp/test.tsv.gz', index=False)
ee = load_dataset('csv', data_files=['/tmp/test.tsv.gz'], delimiter='\t', split='train', download_mode=GenerateMode.FORCE_REDOWNLOAD)
print(ee)
pd.DataFrame(range(10), columns=['numerals']).to_csv('/tmp/test.tsv.gz', index=False)
ee = load_dataset('csv', data_files=['/tmp/test.tsv.gz'], delimiter='\t', split='train', download_mode=GenerateMode.FORCE_REDOWNLOAD)
print(ee)

```

## Expected results
Dataset({
    features: ['numbers'],
    num_rows: 5
})
Dataset({
    features: ['numerals'],
    num_rows: 10
})

## Actual results
Dataset({
    features: ['numbers'],
    num_rows: 5
})
Dataset({
    features: ['numbers'],
    num_rows: 5
})


## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.8.0
- Platform: Linux-4.14.181-108.257.amzn1.x86_64-x86_64-with-glibc2.10
- Python version: 3.7.10
- PyArrow version: 3.0.0
 
 Hi ! Thanks for reporting. The error seems to happen only if you use compressed files.

The second dataset is prepared in another dataset cache directory than the first - which is normal, since the source file is different. However, it doesn't uncompress the new data file because it finds the old uncompressed data in the extraction cache directory.

If we fix the extraction cache mechanism to uncompress a local file if it changed then it should fix the issue.
Currently the extraction cache mechanism only takes into account the path of the compressed file, which is an issue.