Update Rust guidelines for crate-specific errors

[heaths]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the Rust guidelines to provide clearer guidance on handling crate-specific errors in Azure SDK libraries. The changes clarify that crates can return or convert errors into azure_core::Result<T>, and add a new section detailing when and how to implement crate-specific error types.

Key Changes:

• Modified the core error requirement to allow conversion into azure_core::Result<T>
• Added comprehensive guidelines for implementing crate-specific error types when domain-specific information must be exposed

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[heaths]

@weshaggard can you override? A Go aka.ms link is broken and someone just needs to fix it (I hear someone is aware already), but should not hold up other languages.

[heaths]

@gracewilcox made a new link, the but the old link needs to be fixed. I grepped for it and there are dozens if not hundreds of locations. @weshaggard please override. She sent a message to the owner to fix the old one. Hypothetically, aka links should never be broken for more than a short time - we shouldn't replace them, or at least point old vanity ones at new vanity ones.

[heaths]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[weshaggard]

I fixed the go aka links earlier today.