Change predict() generation for non-HMC algorithm to incorporate specified link function

[alizma]

Though it is planned to generalize generate_quantities so that the method does not require an MCMC sample in a near-future Stan release, this package's predict() should generate quantities, with reference to the specified link function, from Python's provided distributions.

The method also doesn't default correctly with discrete families at time of writing this issue...

[WardBrian]

This will be available in Cmdstan 2.31 (see stan-dev/cmdstan#1106) so I’d call it pretty low priority