Proposal: `Iterator::try_flat_map()` method about itertools

[Philippe-Cholet]

I am a bit reluctant to add many methods for fallible iterators because it seems to open the door for many many cases.
However, I reckon that this can not be easily written with Itertools::process_results? Something like that maybe

iter.process_results(|t_it| t_it.map(try_flat_map).process_results(|u_it| ...))??

You have an iterator of results then you map the "ok" values to another iterators of results, then this is flattened, am I right?
It seems to do a lot.

Do you have an usage example for this?

[Niedzwiedzw]

process_results - I've never heard of it, I'll experiment with it, thanks! as for my use case, I needed something like this for recursively iterating a tree of elements and extracting each child is fallible