The test `--test-show-details=direct` switch should imply `-j1`

**Describe the bug**

I like using the `--test-show-details=direct` switch because I see my test output **and** the colours in the test output are preserved. However, if there are more than one test suite, the test suites trash each other's output.

**To Reproduce**
Using cabal-install 3.0.0.0 from git:
```
$ git clone https://github.com/erikd/wide-word
$ cd wide-word
$ cabal build
$ cabal test --test-show-details=direct
```

**Expected behavior**

The tests should be run one at a time so their output doesn't interleave.

**System informataion**
N/A

**Additional context**
N/A

I am going to have a stab at fixing this.