The tests in <nixos/tests/installer.nix> are using `parted`, so they are
bound to be better tested than `fdisk`.
This is brought on by a couple issues, plus reports on IRC that the
`fdisk` instructions didn't work as expected.
* #39354
* #46309
* #39942
* #45478
Care was taken so that the other documented steps did not need changes.
In all this kerfufle, a slight re-organization of the Chapter has been
made, allowing better deep linking.
6cfbf403ca