See #7846

@citibeth this is intended to address:

At this point, a change to the grammar is required so the YAML files can accommodate Spack Setup functionality. I don't know how to change the grammar appropriately.

But it is not complete: it only handles managing the configs and doesn't actually write the spconfig files etc. Depending on your time/preference, this can be folded into #7846 or I can add the rest of #7846 to this.

Allow user specs to store spec as well as a set of packages in the DAG to manage manually; update install/add commands with --setup option

This assumes that the spack.yaml stored for environments maintains user specs either as

spack:
  specs:
    - py-numpy
    - openblas

(as before) or as

spack
  specs:
    - spec: py-numpy
      setup: [python]
    - spec: openblas
      setup: []

This follows the existing environment schema definition (which allows for strings or dictionaries).