Add chirp-mass and mass-ratio prior which are uniform in component masses

This MR is to implement the prior of mass ratio for the case where the uniform prior on component masses is applied while mass ratio is sampled.

The analytic expressions of its PDF and CDF are given in https://git.ligo.org/soichiro.morisaki/utilities/-/blob/master/mcq_sampling_bilby/mcqprior.pdf .

It has been tested in https://git.ligo.org/soichiro.morisaki/utilities/-/blob/master/mcq_sampling_bilby/CheckNewAnalyticPrior.ipynb .

cc: @colm.talbot