Pseudo-cl covariance from Gaussian simulations

[sachaguer]

In the non-tomographic UNIONS analysis, the iNKA covariance was validated against Gaussian simulations produced from the catalogue.

The production of the pseudo-cl samples for the computation of this covariance was made with an independent script where the hyperparameters were hard-coded. This issue aims to:

• Extend the script to tomography. This should be a straightforward call to the functions implemented within Reopen: Tomographic pseudo-cl #240 .
• Make the call to the script generating the Gaussian simulations more systematic with proper configuration.