The stock `Terraform-Module` template from GitLab defines its own stages
which are _almost_ compatible with Auto DevOps but not quite.

Issue #59 initially proposed re-working `terraform-module.yml` to be
based on the base template but, really, the only thing that needed to be
done was to move the `fmt` job from the `validate` stage to `test`.

(Arguably `fmt` could be replaced by stuff from
`/auto-devops/terraform-pipeline.yml` but that's for another day.)

Instead of copy-pasting the module, simply import the Auto DevOps stages
and move the `fmt` job.

While we're here, and because this is supposed to be "the One Template
To Rule Them All" for terraform modules, also add in a default
`workflow` template *a la* `common-pipeline.yml`.