feat: enable ARM64 Linux runners in CI matrix

[crStiv]

Motivation

The CI matrix had a TODO comment for ARM64 Linux support due to the lack of native GitHub ARM runners. Previously, ARM64 testing required slow QEMU emulation. GitHub recently made ARM64 runners (ubuntu-24.04-arm) available for free in public repositories (January 2025), making native ARM64 CI testing possible.

Solution

• Remove TODO comment and enable ARM64 Linux runner target
• Use ubuntu-24.04-arm runner label with aarch64-unknown-linux-gnu target
• Include ARM64 in CI matrix for push events only (not PRs for cost efficiency)
• Add documentation comments explaining the ARM runner availability

PR Checklist

• Added Tests (script generates matrix configurations, no additional tests needed)
• Added Documentation (inline comments added)
• Breaking changes (backward compatible addition)

[DaniPopes]

Thanks took over in #11386