`cabal test` slow because of lack of caching

**Describe the bug**
`cabal test` is slower than running `cabal run tests` when nothing has changed. This issue is exacerbated when using the new [code generators](https://github.com/haskell/cabal/pull/7688) feature, which makes cabal recompile the test suite on every invocation.

**To Reproduce**

Clone https://github.com/gbaz/cabal-doctest-demo.
```bash
$ cabal v2-test
```
Running the second time still recompiles the test suite.
```bash
$ cabal v2-test
```

**Expected behavior**
Cabal should not recompile the entire test suite when nothing has changed.

**System information**
- NixOS 22.05
- Cabal 3.8.1.0
- GHC 9.2.4