Fix ARM workflow runner routing

[simongdavies]

Summary

Removed the ubuntu-24.04 label from ARM jobs in preparation for remvoing the label from the self-hosted runners (the presence of this label caused any job that uses ubuntu-24.04 as a runs-on label to potentially target the ARM runners.

Also fixed a bug where examples were being run on kvm instead of hvf.

• ARM Linux selectors use the built-in OS and architecture labels, with kvm where required. Guest builds need no hypervisor label.

• ARM HVF examples run on native macOS runners using the shared metrics and logging recipe.

• macOS Rust cache cleanup excludes shared Cargo binaries, matching the build-test workflow.

[Copilot]

🟡 Changes recommended

The new ARM HVF selector uses macos instead of macOS, which can prevent jobs from matching any runner labels and block workflow execution.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Updates GitHub Actions runner selectors to route ARM jobs using simplified label sets (dropping ubuntu-24.04), and adjusts ARM HVF example execution to target native macOS runners while keeping existing Linux coverage.

Changes:

• Remove ubuntu-24.04 from multiple ARM self-hosted runs-on label sets (and drop hypervisor label for guest builds).
• Route ARM example runs based on hypervisor (HVF → macOS, KVM → Linux) and split example execution per OS.
• Adjust Rust cache behavior to avoid ~/.cargo/bin cleanup/caching issues on macOS runners.

File summaries

File	Description
.github/workflows/PrimeCaches.yml	Drops ubuntu-24.04 from ARM KVM runner labels for cache priming.
.github/workflows/dep_run_examples.yml	Routes ARM runs to macOS for HVF vs Linux for KVM; updates cache-bin and OS-specific example steps.
.github/workflows/dep_fuzzing.yml	Drops ubuntu-24.04 from ARM KVM runner labels for fuzzing.
.github/workflows/dep_build_guests.yml	Drops ubuntu-24.04 and hypervisor label from ARM guest build runner labels.
.github/workflows/dep_benchmarks.yml	Drops ubuntu-24.04 from ARM KVM runner labels for benchmarks.

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 1
• Review effort level: Lite

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[dblnz]

Looks good to me, with a single question in the comments!