Name options for simulate_summary()

[jamesmbaazam]

Would it help to rename simulate_summary() to say, sample_tree_metrics()? This would then reserve 'simulate' for code that gives the tree structure. However, running summary(simulate_tree()) should also give the same-ish output as sample_tree_metrics() for the same ntrees and offspring_dist.

It's not really sampling. The current simulate_summary() function is running a stripped down version of simulate_tree() that only returns the chain_statistic of interest without tracking related information. Speaking out loud now, I think it's probably better to rename it to simulate_statistic(). I mentioned in the second bullet of #79 that the name simulate_summary() would need some reconsideration.

Originally posted by @jamesmbaazam in #107 (comment)