Initial replacement for CI/CD stage

[ludoo]

This moves CI/CD repository creation to a new extras folder, and only supports a single provider per extra stage, in this case GitHub.

The stage creates repositories, allows initial configuration (.gitignore, etc.), and also optionally pushes files replacing modules source if a repo module is created too.

It's only intended to be used for initial repo creation and population, as committing files will potentially overwrite any changes.

An example tfvars file:

organization = "ludomagno"
repositories = {
  fast_00_bootstrap = {
    create_options = {
      description = "FAST bootstrap."
      features = {
        issues = true
      }
    }
    populate_from = "../../stages/00-bootstrap"
  }
  fast_01_resman = {
    create_options = {
      description = "FAST resource management."
      features = {
        issues = true
      }
    }
    populate_from = "../../stages/01-resman"
  }
  fast_02_networking = {
    # populate_from = "../../stages/02-networking-peering"
  }
  fast_modules = {
    has_modules = true
  }
}