The old string format is a holdover from the pre JSON days. It is not
friendly to users who need to get the information out of it.
Also introduce the sort of versioning we have for derivation for this
format too.
Now that we have a few things identifying content address methods by
name, we should be consistent about it.
Move up the `parseHashAlgoOpt` for tidiness too.
Discussed this change for consistency's sake as part of #8876
Co-authored-by: Eelco Dolstra <edolstra@gmail.com>
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/
```
