Add `cabal-testsuite` as package for changelogs

**Describe the feature request** Can we produce changelogs for `cabal-testsuite`? It is an important part of the project. This would be for changes in these modules: ```pre $ tree cabal-testsuite/src/Test cabal-testsuite/src/Test └── Cabal ├── CheckArMetadata.hs ├── DecodeShowBuildInfo.hs ├── Monad.hs ├── NeedleHaystack.hs ├── OutputNormalizer.hs ├── Plan.hs ├── Prelude.hs ├── Run.hs ├── Script.hs ├── Server.hs ├── TestCode.hs └── Workdir.hs ``` I tried doing that and got this error: ```yaml --- synopsis: Something changed with the test suite? packages: [cabal-testsuite] --- ``` https://github.com/haskell/cabal/actions/runs/28534834398/job/84593427631?pr=12069 ``` Validation error(s) in entry `changelog.d/12069.md`: Unknown package cabal-testsuite error: Validation failed. ```