Update event bus OEP

[robrap]

AC:

• [x] OEP-52 should be reviewed/updated to bring up-to-date.
  • [x] Possibly summarize/note new ADRs? (See other ADRs already in the OEP for examples.) The point is not to change the main point of the OEP, but simply to provide more details if they make sense at the level of the OEP.
  • [x] Provide link in new header to Roadmap/Next Step for moving from Provisional to Accepted, as now documented in OEP-1.

Notes:

• https://open-edx-proposals.readthedocs.io/en/latest/architectural-decisions/oep-0052-arch-event-bus-architecture.html

[robrap]

@rgraber: I'm going to unblock this task. See my latest comments https://github.com/openedx/open-edx-proposals/pull/414#pullrequestreview-1199995495. If you disagree, we can discuss and determine whether to block again.

[rgraber]

Closed by https://github.com/openedx/open-edx-proposals/pull/414