Refactor test resources and create resource struct

The test code should not be using a custom resource type which in turn must be created into the Resource types used by manifests.

```
r, err := Declare(Resource{
Kind: RegularFile,
Path: "/foo",
})
```

And for tests

```
[]Resource{
MustDeclare(Resource{
Kind: RegularFile,
Path: "/foo",
}),
}
```

Referenced from https://github.com/stevvooe/continuity/pull/14#discussion_r49527966