RFC 311: Add site-admin UI page to view migrations
Created by: efritz
This adds a UI Page to site-admin that shows the current progress of out-of-band migrations. This fixes https://github.com/sourcegraph/sourcegraph/issues/18239 and I'm pushing this to get out to make it obvious when out of band migrations are not working properly (and why!) in our cloud environments as we're getting an increasing number of users.
Current development environment screenshots:
I'd like to rope in @sourcegraph/design once they have the bandwidth to work on more internal-facing (developer troubleshooting) areas of the application.