Add attrs if `adapt_freq`, `jitter_under_thresh` are used

[coxipi]

Adjustment methods that allow adapt_freq_thresh and jitter_under_thresh should maybe keep the information of the parameters (other than the general xsdba history)

[coxipi]

I had forgotten that adapt_freq_thresh is now conserved with the changes to the frequency adaptation.

In the case of jitter_under_thresh, could I classify this as a parameter similar to e.g. the number of quantiles? I don't think we'd want to keep an attr for every param currently, so I changed my mind. I think that having the information in the history is sufficient. If in the future, we need to preserve the jitter-under-thresh value e.g to apply it again in the adjust part, we will add this to what the class keeps.

So I'm thinking this should be closed, but I'll wait to have someone's take on this