Explore Lazy Iterators.accumulate usage

[SamuelBrand1]

As part of #369 review we identified an alternate accumulate method provided by Base.Iterators that returns a lazy version of accumulate.

This has potential upsides; for example data annealing SMC/particle filtering, e.g. constructing the target posterior distributions as a sequence over increasing data/data batches. The advantage here could be only using elements of accumulate return needed for log-like calculation upto a time horizon.