`cabal test` outputs stdout and stderr out of order

With https://github.com/hdgarrood/cabal-test-stderr, if you run `cabal test`, you get this:

```
Preprocessing test suite 'tests' for cabal-test-stderr-0.1.0.0...
Running 1 test suites...
Test suite tests: RUNNING...
oops, failed
lol
Test suite tests: FAIL
Test suite logged to: dist/test/cabal-test-stderr-0.1.0.0-tests.log
0 of 1 test suites (0 of 1 test cases) passed.
```

But if you run the test executable directly, you get this:

```
lol
oops, failed
```

That is, `lol` and `oops, failed` appear the other way around.

The source code is:

```
import Control.Monad
import System.IO
import System.Exit

main = do
putStrLn "lol"
hPutStrLn stderr "oops, failed"
exitFailure
```

I expected `cabal test` to produce text output in the same order as running the executable directly, even if the test executable outputs text to both stderr and stdout.

Possibly related: #1601. Being able to easily run the test suite directly would make this less of a problem.

Reproduce the ordering difference with the Haskell program in the issue, comparing `cabal test` with running the test executable directly. Start at the `cabal test` path and the related discussion in #1601; done means stdout and stderr appear in the same order under Cabal as they do from the executable.

Written by the indexing model from the issue text.