RFC 697: Isolate out-of-band migrations (code intelligence)

Created by: efritz

See RFC 697: Multiple version upgrades.

Update out of band migrations #1, #4 and #5, #7, #8, #11, and #12 so that they do not require code outside of a specific allow-list (which excludes things like the gitserver client, which we'll have to engineer around). Note that all migrations, at a glance, seem to already conform to these requirements except for #8.