Consider renaming pole_density_function to pole_density_distribution

[harripj]

I think perhaps it would be quite informative as to rename pole_density_function to pole_density_distribution, as in these functions we are computing the quantitative density distribution rather than internally creating a functional representation of the pole distribution. Perhaps the new function name would be more clear for the user and more representative for those inspecting the code.

[hakonanes]

Sounds good to me. We can deprecate the former in v0.12.0 and point to the latter, with removal in v0.13.0.