[Fix] decode URL encoded string in config path

[kbumsik]

Motivation

Some packages has config paths which is url encoded (e.g. %2B for +) https://github.com/open-mmlab/mmdetection/blob/db85fd12afce2fe89d1c7b870874c02a90018a16/configs/gn%2Bws/metafile.yml#L17

Currently downloading those models trrigers "is not found" error because mim does not support url encoded path.

Modification

While I am not sure if this should be fixed in mim or in metafile.yml in the package, I firstly attempt to fix in mim package.

BC-breaking (Optional)

Use cases (Optional)

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMCls.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[ice-tong]

Hi @kbumsik, thanks for your kind contribution!

The Config field in Metafile.yml actually should be a file path.

The URL encode in Config path is not a normal behavior, and we will check with mmdetection.

Thanks again!

[kbumsik]

I see, then do you prefer closing this?

I actually fixed all of metafile.yml in mmdetection, including url encoded file paths: open-mmlab/mmdetection#9627

[ice-tong]

@kbumsik Sorry for the late reply~

I prefer to close this PR, and feel free to reopen it if you have any problems. ^_^