Sample parameters from prior distributions
sample_priors.RdDraws one candidate parameter set:
amp_rate / del_rate / bfb_prob as relative proportions from a symmetric Dirichlet(1,1,1) — uniform on the 2-simplex.
death_rate as a fraction of birth_rate, uniform on (0, 0.8).
lambda (mean genomic events per daughter cell) uniform on (0.5, 5).