This function maps a user-specified distribution name to a list containing the names
of the corresponding density and random generation functions. If the distribution
is not explicitly mapped, it assumes the standard naming convention by prepending
"d" or "r" to the distribution name.
get_dist_names(distrib)A list with components d and r, which are character strings
representing the names of the density and random generation functions, respectively.
A character string specifying the distribution.
get_fitdist_name