Add methods to test the toolchain

The 23b toolchain right now dosent install libxc even though its in the environment definition. See spack-environments#40 (closed)

It would have gone unnoticed that this package was not installed. It makes sense to have a test command that tests that the installed toolchain meets certain expectations for eg:

• selected few packages are present as expected
• Lmod modules are loadable ( including the order of packages etc )
• compile a small tet program?
• etc