ENH: proportion_confint only has two-sided confidence intervals, no "alternative" option

[josef-pkt]

see https://stats.stackexchange.com/questions/646445/multinomial-one-sided-confidence-intervals

same for multinomial_proportions_confint

I think for proportion_confint it should be just one interval at 2*alpha, except for "beta-test" which is minlike, and the one-sided will correspond to one side of equal-tail intervals.

I don't have a guess on one-sided interval for multinomial_proportions_confint. (too long ago). But it might be based on an equal-tail derivation.