Add utility for verifying that version/variant/externals are respected

[AlexanderRichert-NOAA]

Summary

This PR adds a utility for verifying the concretized environments respect the configured version (common/packages.yaml), variant (common/packages.yaml), and external (site/packages.yaml) settings.

Testing

Tested on personal machine and in util_tests.sh/CI. Will explore adding to build CI.

Applications affected

none

Systems affected

Should be useful on all systems, though as currently written, it might involve ignoring certain packages on certain systems.

Dependencies

none

Issue(s) addressed

Link the issues addressed or resolved by this PR (use Fixes #??? for fully resolved issues)

Checklist

• This PR addresses one issue/problem/enhancement, or has a very good reason for not doing so.
• These changes have been tested on the affected systems and applications.
• All dependency PRs/issues have been resolved and this PR can be merged.

[AlexanderRichert-NOAA]

@climbfuji I decided not to put it in the main CI since I think the utility of it is more for telling an installer "hey just so you know," but I'm open to adding it. I think it would take a bit of work since when I tried it there were maybe a dozen or so packages that didn't match the configuration (but I don't know how much of that is intentional).

[climbfuji]

This is a handy tool, thanks for coming up with this. Two questions:

1. How are variant mismatches for externals handled? I believe spack concretize just uses the variants specified for the external when it uses it, correct? (same for version)
2. Would it be better to use a repetitive -i (ignore) flag for ignoring certain packages like esmf? This way it would be more consistent with the show_duplicate_packages.py script, and it would also be more intuitive. The current syntax is more commonly used to check for just this package, not all others except that?

[AlexanderRichert-NOAA]

1. Correct (i.e., we don't need a separate check because the concretized spec will be constrained by the external spec).
2. Done. The ubuntu ci is failing with some kind of git/runner-related glitch but otherwise I think the updated code works.

[climbfuji]

Thanks for considering my comments and suggestions!

I restarted the failed CI run and enabled auto-merge

[AlexanderRichert-NOAA]

@climbfuji cool. FYI I (finally) added the util-tests as required just now.