gh-404: Implement mochi class emulator

[LisaGoh]

🚀 Pull Request Checklist

✅ Summary

This PR solves issue #404.

🔄 Changes

Incorporated an emulator for the linear power spectrum calculated by mochi_CLASS (the mochiCLASSEmuLinearPerturbations class), trained using Cosmopower. Currently, it is implemented for the stable basis parametrisation of Lombriser et al. 2019 (varying s, a0, a1) + w0wacdm background (w0,wa), for fixed cosmology parameters (Planck 2018 fiducial). It currently only returns the linear matter power spectrum (no sigma8, nor fsigma8).

🛠 How to Test

📝 Documentation

• This PR updates documentation
• This PR does not require documentation changes
• Issue created for documentation update: Don't forget to link the task!

🏗 Related Issues

Resolves #404

📸 Screenshots (if applicable)

📌 Additional Notes

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[gcanasherrera]

This needs to be updated when #352 is merged.

[LisaGoh]

Heyoo @gcanasherrera I've updated this branch since #352 is now closed!