Tracking Issue for Iterator fold_mut

[mlodato517]

This is a tracking issue for the fold_mut method in the Iterator trait defined in #76746.
The feature gate for the issue is #![feature(iterator_fold_mut)].

Steps

• Implement fold_mut (Add fold_mut alternative to Iterator trait #76746)
• Adjust documentation
• Stabilization PR

Unresolved Questions

1. Should we instead put this effort into optimizing the existing fold method?
2. Why is the existing fold method any slower?

Implementation history

Implementing fold_mut - #76746