Static files and zip content cleanup

[rtibbles]

Summary

• Uses Whitenoise for all static file serving
• Removes use of collectstatic command and associated options.ini option
• Adds static file serving to alternate origin server
• Cleans up dead code for H5P serving that is obsolete with static file serving

Reviewer guidance

Do static files always load?
Do H5P files still render properly?

References

Fixes #7917
Fixes #7792

Screenshot of now functional swagger API explorer:

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Contributor Checklist

PR process:

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Testing:

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

Reviewer Checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[jonboiser]

Looks good! DRF APi Explorer, Swagger API explorer, static assets, and H5P work fine.