Describe the bug
As a dev team, we are failing in spotting PVP breakage.

To Reproduce
Last Cabal release (3.12.1.0) was a minor one (that is from from 3.12.0.0 to 3.12.1.0).
This means no PVP breaking changes should have been introduced.

Alas, at least two of those breaking changes are present in the release, see PRs #9766 and #9878. Both those PRs introduce a new constructor, hence the backport actually changed the API for Cabal.

Expected behavior
We don't let breaking changes slip in minor cabal releases, be it with the help of a checklist or automated testing or anything else (suggestion welcome).