Revert "Replace pkg_resources with importlib.resources"

[jesperhodge]

Before merge:

• This needs to be tested in a stage/prod like environment
• Needs some assessment of the risks involved in deploying it
• At minimum this needs the edx-platform pipeline on 2U's side paused and a smoke test in stage

Description:

This PR reverts a change which appears to have caused the unit pages of different courses not to work on stage and prod. The bug started right after the change was deployed (January 23) and relates to code that was modified.

Context:

https://openedx.slack.com/archives/C0497NQCLBT/p1738607786863749

Internal TNL Links:

• https://2u-internal.atlassian.net/browse/TNL-11867
• https://2u-internal.atlassian.net/browse/CR-7277
• Slack discussion
• Datadog Errors

Steps to reproduce bug (on stage or prod):

• Not reproducible locally because local asset urls are different anyway
• Go to a stage or prod environment
• Create a drag-and-drop component (or poll, survey, or anything not core)
• Load the unit page (shows loading spinner)
• Try to edit the drag-and-drop component (cannot edit or save)
• Add a problem block after the failed component
• That problem block will also not load

Causes:

• CMS calls to /static/studio/xblock/resources/... produce 404s
• The PR to revert modifies code that relates to providing / accessing these xblock resources

Reverts #36044

[jesperhodge]

Currently testing this locally.

[jesperhodge]

Tested locally. Don't see any immediate problem so we can proceed to next step (SRE risk assessment).

[jesperhodge]

I changed this to draft so it doesn't get merged by accident.
We do not deem this safe enough to deploy at this time.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.