feat: Implements retrying logic for downloading models using --model-url flag

[farbodbj]

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This PR implements the improvement requested at #6288, the approach is simple and uses a while loop for retrying with exponential backoff.
I found two calls to curl_easy_perform which is the function responsible for transferring the data, and on the call sites, I added the while loop for retrying on the condition of failing.
For now, the retry count is fixed as a local variable inside the function, but passing the retry count as a CLI argument can further improve this feature.
I compiled the project after the changes with make LLAMA_CURL=1 and tested it both with and without internet connection and it worked okay.
It's my first time working with curl API in cpp so any suggestion for improvement is appreciated.

[farbodbj]

@ngxson
I applied your comments. wasn't sure where I had to put my #defines so I put them right above the function using them.

[farbodbj]

I would also appreciate if someone can help me to fix the editorconfig-checker CI job, I couldn't figure out how to run the job locally to fix formatting and white space problems

[slaren]

I would suggest extracting the retry logic to a function rather than duplicating the code.

[farbodbj]

I would suggest extracting the retry logic to a function rather than duplicating the code.

I agree on that. Do you suggest I do it in this PR or do it later? I think approving will be required again after i apply the change

PS: Done 😄

[slaren]

@ngxson Please update your review.

[ngxson]

Thanks. I'll merge when CI passes