Rename sample_prior_predictive argument from samples to draws

[ricardoV94]

Description

sample calls it draws, and the default dim is also draw. Whenever I want to use a kwarg to specify the number of draws I am always surprised it's called samples. Does everyone agree?

If so we could rename and add a futurewarning for the old arg name.

Or make everything samples... just use the same arg name please :)