Implement ignore function on Result. Fixes #20949

[sixohsix]

I decided to implement a fix for #20949, which adds a .ignore function to Result, because it seemed easy and fun to do. However, I'm I'll defer to Rust core devs to decide if they even want this feature. If you don't want this feature, no problem, just close the PR.

This is my first pull request, so please review mercilessly, and let me know if I should change anything.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon.

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[alexcrichton]

Thanks for the PR! At this time we're focusing on stabilizing what we currently have in the standard library for the upcoming 1.0 release, and for now we're trying to cut back on various APIs throughout the libraries. In the future we're likely going to require an RFC for new APIs, especially those on core types like Result.

At this time I don't think that there's a wide enough consensus that we want this function, and adding it is certainly backwards compatible! If you'd like to pursue this, I'd recommend opening a discussion thread on discuss.rust-lang.org or perhaps an RFC to canvas other opinions on whether we should add this method.

For now though I'm going to close this, but thanks again for investigating it!