Added Agauss, Zagauss and Zgauss

[CamilleDiez]

Added redshifted gaussian in energy space (Zgauss) + simple and redshifted gaussian in wavelength space (Agauss and Zagauss). Removed primitive definition in Gauss + small changes for harmonization between all gaussian models.

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📚 Documentation preview 📚: https://jaxspec--122.org.readthedocs.build/en/122/

[codecov[bot]]

Codecov Report

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

Comparison is base (a82d9f8) 89.13% compared to head (12b5260) 89.42%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #122 +/- ## ========================================== + Coverage 89.13% 89.42% +0.29% ========================================== Files 17 17 Lines 1003 1031 +28 ========================================== + Hits 894 922 +28 Misses 109 109 ```

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