Created new `tests/format/iteration.py` which tests the order in
which elements are iterated over in various scopes in a loaded
data model.

The tests/format/project.py test already has some tests about how
we error gracefully for bad plugins and bad plugin configurations,
lets put it there rather than tests/pipeline/load.py which we
will remove.

This is where other load time related plugin error handling is
checked, and is the last thing to remove in the `tests/pipeline`
directory.

Remove some redundancy from the test lines.

The remaining test simply loads a project with one element
and asserts a value on it. This is already sufficiently tested
in tests/format/project.py.

This is the directory for all things related to loading.