Consolidate Gaussian1 functors

[ischoegl]

Changes proposed in this pull request

• Use C++ Gaussian1 functors instead of Python implementations in samples and tests
• Use underscores rather than the unpythonic hyphens ("kebab-case") in the new nanosecond-pulse-discharge.py sample
• Use snake_case rather than the unpythonic CamelCase for PorousMediaBurner.py and NonIdealShockTube.py samples

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

Closes #1950

Checklist

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

[ischoegl]

Sample runners are failing due to Cantera/cantera-example-data#3. Otherwise, this is ready for a review.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.98%. Comparing base (3375822) to head (970fb1e).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1951      +/-   ##
==========================================
+ Coverage   74.97%   74.98%   +0.01%     
==========================================
  Files         450      450              
  Lines       56241    56241              
  Branches     9300     9300              
==========================================
+ Hits        42168    42174       +6     
+ Misses      10939    10933       -6     
  Partials     3134     3134              

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[speth]

For these two existing examples, it would be helpful to add redirects for these names to the .htaccess files in the cantera-website repository.

[ischoegl]

👍 ... see Cantera/cantera-website#276

[ischoegl]

@speth ... sorry to dismiss your review, but I decided to test the new example-data procedure (while also addressing the license issue). The merge sequence would thus be:

1. Clarify readme (Cantera/cantera#1951) cantera-example-data#5
2. this PR
3. Update snake_case Python sample redirects cantera-website#276

[ischoegl]

@speth ... the example_data submodule is reset.