fix(q_dev): Add validation for empty S3 CSV file list

[DiscreteTom]

⚠️ Pre Checklist

Please complete ALL items in this checklist, and remove before submitting

• [x] I have read through the Contributing Documentation.
• [x] I have added relevant tests.
• [x] I have added relevant documentation.
• [x] I will add labels to the PR, such as pr-type/bug-fix, pr-type/feature-development, etc.

Summary

What does this PR do?

• Throw BadInput error when no CSV files found in S3 path
• Helps users identify incorrect S3 bucket/prefix configuration
• Extract functions for unit tests
• Add unit tests

Does this close any open issues?

Closes xx

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Other Information

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