Automatically set code owner for all celery tasks

[timmc-edx]

Update: This didn't work, so we're updating the ADR to at least describe why we can't use this approach: openedx/edx-django-utils#345

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We currently have to annotate individual Celery tasks with a decorator in order to get code-owner information. This causes Arch-BOM to get alerted sometimes due to missing decorators on new tasks. We've since learned of an alternative approach involving a signal, documented in ADR 3 of edx-django-utils.

• Add a new signal receiver on task_prerun that sets a new custom attribute with the module of the task
  • feat: Add an experimental custom attr for automatic Celery task code owner #33180 but reverted in Revert "feat: Add an experimental custom attr for automatic Celery task code owner" #33272 because this didn't pan out. See comments.
• Confirm using New Relic that the new custom attribute matches the existing code_owner values, with no gaps
• Change the receiver to call edx-django-utils set_code_owner_attribute_from_module
• Remove explicit set_code_owner_attribute and set_code_owner_attribute_from_module calls/decorators from tasks in edx-platform

[gautammd]

@timmc-edx can I have a go at this?

[timmc-edx]

You can give it a try, but my experimental change in #33180 didn't work. I think New Relic opens the transaction after task_prerun and closes the task before task_postrun, so this signals-based approach probably doesn't work.