[Docs] Add OpenBao diagrams to design document
The design document should continue to be the single source of truth for architecture information.
We created several new diagrams during the offsite:
- https://gitlab.com/gitlab-org/govern/secrets-management/deployment-investigation/-/issues/2
- https://gitlab.com/gitlab-org/govern/secrets-management/deployment-investigation/-/issues/3
These should be imported into the design document for posterity.
We should also update the ORR to reference these new diagrams.
Edited by Alex Scheel