Need better python management

[dgarciabriseno]

There are currently 4 requirements.txt files in this repo, a couple dependabot PRs that I need to work on for them, and there is not one for downloader.py which keeps images flowing in to helioviewer.

I also recently pushed a change which broke the downloaders since the change updated a script to work in the CI pipeline, but did not work on the helioviewer server since the server was running an older version.

What is the best practice for keeping dependencies up-to-date?