Rename `max_split` parameters.

[pshriwise]

There's currently a max_split parameter on both the Settings and WeightWindow classes. The parameter on settings limits the number of times a particle can be split over its entire history and the other limits the number of splits per weight window chcek.

Renaming these parameters for to distinguish them by their purpose would be helpful.

[shimwell]

How about lifetime_max_splits and max_splits_per_ww

[paulromano]

Closed by #2954