Replace django-celery with django-celery-results
Upgrade redis to latest

Fixes styling issues

Revert "ARCHBOM-1494: Refer to custom attributes, not metrics, especially with edx-django-utils (#25010)" (#25025)

This reverts commit ba9ee4e1.

Fixed Style lint issue

This uses the new names introduced in edx-django-utils
3.8.0 (edx/edx-django-utils#59), which we're already using, as
well as updating a few other locations where we incorrectly refer
to New Relic custom metrics instead of custom attributes.

Includes a couple of unrelated lint fixes in a file I modified.

MST-418 retire program_enrollments external_user_key with hashed values instead of setting it to null (#25001)

ENT-3328

MST-406 Update the proctoring library so we can prevent learners from creating exam attempts on past due exams (#24918)