The state manager refactoring in an earlier commit was reflected in the
implementations of these backends, but not in their tests. This gets us
back to a state where the backend tests will compile, and gets _most_ of
them passing again, with a few exceptions that will be addressed in a
subsequent commit.
The new config loader requires some steps to happen in a different
order, particularly in regard to knowing the schema in order to
decode the configuration.
Here we lean directly on the configschema package, rather than
on helper/schema.Backend as before, because it's generally
sufficient for our needs here and this prepares us for the
helper/schema package later moving out into its own repository
to seed a "plugin SDK".
Martin Atkins