Add option to generate mock data from Sherwood sim

[andreufont]

It would be pretty cool to have a mock data vector from the Sherwood simulation (probably from the L80_N2048 box). We measured this in the Sherwood paper (Givans et al. 2022), so it should be easy to do. The only difficulty is that we don't have many redshifts available, but even if we only had 4 of them it would be a cool test (we could artificially shrink the covariance matrix to compensate the lose of redshifts and keep a similar constraining power).

I imagine that the analysis will be quite complex, however, since the IGM history in the sim might be quite different than the ones in the Australia20 suite used by LaCE. We would like to have an IGM model that is flexible enough to accommodate many IGM histories (we don't know the real one in the Universe!), so this is definitely something we want to test eventually, but it might require some improvements on the likelihood code (and many free parameters).

[andreufont]

A similar test would be to analyse the "P18" simulation already present in the Australia20 suite, that has a very different IGM history (it uses the files from Puchwein et al. 2018).