This progress on #11896. It introduces some issues temporarily which
will be fixed when #11928 is fixed.
The SQL tables are left in place because there is no point inducing a
migration now, when we will be immediately landing more changes after
this that also require schema changes. They will simply be ignored by in
this commit, and so all data will be preserved.
I think it is bad for these reasons when `tests/` contains a mix of
functional and integration tests
- Concepts is harder to understand, the documentation makes a good
unit vs functional vs integration distinction, but when the
integration tests are just two subdirs within `tests/` this is not
clear.
- Source filtering in the `flake.nix` is more complex. We need to
filter out some of the dirs from `tests/`, rather than simply pick
the dirs we want and take all of them. This is a good sign the
structure of what we are trying to do is not matching the structure
of the files.
With this change we have a clean:
```shell-session
$ git show 'HEAD:tests'
tree HEAD:tests
functional/
installer/
nixos/
```
