Fix Python sdist issues

[speth]

Changes proposed in this pull request

• Fix installation of YAML data files in the Python sdist
• Simplify command line interface for building the sdist
• Speed up CI by using micromamba
• Remove test code from coverage report to avoid inflating apparent coverage

If applicable, fill in the issue number this pull request is fixing

Resolves #1678.

If applicable, provide an example illustrating new features this pull request is introducing

Checklist

• [x] The pull request includes a clear description of this code change
• [x] Commit messages have short titles and reference relevant issues
• [x] Build passes (scons build & scons test) and unit tests address code coverage
• [x] Style & formatting of contributed code follows contributing guidelines
• [x] The pull request is ready for review

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 72.82%. Comparing base (4565a55) to head (e0654b2).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1708 +/- ## ========================================== - Coverage 75.72% 72.82% -2.90% ========================================== Files 443 379 -64 Lines 60981 53592 -7389 Branches 9557 9122 -435 ========================================== - Hits 46178 39031 -7147 + Misses 11777 11610 -167 + Partials 3026 2951 -75 ```

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