RFE: warning about downgrades

[juhp]

Occasionally it can happen that a package is downgraded in version by accident.
eg a dependency bounds issue is misinterpreted as being due to a new version
rather than a change in the other package. A recent example was for tasty-quickcheck
(now fixed again in https://www.stackage.org/nightly-2024-12-08).

Not sure how easy this would be to implement.

Also stackage-server could highlight such downgrades.