Update ckpt loading

[schoi-habana]

PR#15 reads a set of ckpt file names from the index json file.
When OH downloads files from the hub instead of loading from a cache dir, get_repo_root() skips downloading the index json file. Thus the PR#15 fails to load file names.
This PR scans the path and returns a list of names that matches the pattern

Tested the models in cache dir:
Falcon-7b, Falcon-40b, Falcon-180b, Llama-70b

Tested the models downloaded from HF hub:
Falcon-7b, Falcon-40b, TinyLlama

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?

[schoi-habana]

please note that this is to fix errors from #697

[HuggingFaceDocBuilderDev]

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