[Core] Add is_xxx_or for Result and Option

[Embers-of-the-Fire]

These supplements are akin to the current is_xxx_and APIs.

[must_use]

We generally utilize these methods to verify an option or result, thus necessitating the use of must_use.

ACP

ACP is likely to be a trivial task, given that this modification is likely smaller than the accompanying documentation.

[rustbot]

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

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[Noratrieb]

Thank you for the PR! This PR contains a public library API change, which should follow the proper process of creating an ACP first: https://std-dev-guide.rust-lang.org/development/feature-lifecycle.html
Use @rustbot ready when your ACP has been accepeted.

[joshtriplett]

r? libs-api

[Dylan-DPC]

@Embers-of-the-Fire any updates on creating the ACP for this?

[Embers-of-the-Fire]

@Embers-of-the-Fire any updates on creating the ACP for this?

Sorry I've been busy lately and haven't been following the action here. I guess there is a need for a standard RFC process for such small changes? I will prepare it now if needed.

Edit: ACP: ACP

[Embers-of-the-Fire]

@rustbot review