Handle OpenEdX upstream refactor of Tubular retirement scripts from their own repo into the monorepo

[feoh]

Description/Context

I just found out about this OpenEdX PR that moved the retirement scripts out of their own repo.

Since we have downstream changes we (I) never managed to upstream, we'll need to figure out how to handle this.

@pdpinch I know you had other folks working on retirement related stuff and things - did we decide that tubular was too high touch and manual for our needs or should we figure out what to do about this change?

Plan/Design

TBD - Possibly remake our local changes as a PR to the newly relocated scripts and deprecate our own Tubular. They'll have also upgraded those scripts to 3.12 which may make the delta between larger.