Add $ to the end of filename regex patterns

[tomaarsen]

What does this PR do?

• Add $ to the end of filename regex patterns
• add an unrelated test for a model with modeling files in a subfolder and configuration files in the root. This passes on main, but failed on 1.19.0. As expected, if subfolder="openvino", then the OV files can be seen, if subfolder="", then they are not.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

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• Tom Aarsen

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[echarlaix]

Looks good thanks @tomaarsen !