Feature: download_all and download_layer controller

[Sonia-96]

Primary changes in this Pull Request:

• Add download_all and download_layer controller to handle dataset and file download, and add related tests
• Add a Download button on the Files tab of dataset details that allows users to download all files associated with a dataset with a single click.

Please review the checklist before submitting the Pull Request:

• Pull request has a meaning full name (not just the commit message from of your last commit)
• Code has been linted using flake8
• All methods have accurate Google-Style Docstrings
• 100% test coverage for new content
• Tests for each common use case (please don't write one test that covers all use cases)
• Bonus: Use TypeHints

Explain deviations from original design if applicable: