Feature Request: `simulate_chain_stats` with limit on one stat, but reporting both stats out

[pearsonca]

Is your feature request related to a problem? Please describe.
I have a use case where I'm essentially looking to get the outbreak distribution in terms of number of cases, subject to a time constraint.

Describe the solution you'd like
Basically, want to use simulate_chain_stats, with a generation limit, but report size outcomes instead of generations.

I imagine other folks might be interested in the complementary view (limiting by size, what generation gets hit), so probably just generalize to return both.

[jamesmbaazam]

Thanks, Carl. This is a a nice use case worth exploring, so I'll make a plan to fix it in the next release.