Leverage `rb-sys` features for simplified CI and cross-platform builds

[ianks]

This PR updates the project to utilize the latest features and best practices provided by the rb-sys project.

Key changes

• Simplify GitHub Actions workflows by using pre-built actions from oxidize-rb/actions, which will:
  • Use the blessed platforms for rb-sys, in particular this adds support for aarch64-linux
• Replace Rake::ExtensionTask with RbSys::ExtensionTask since it implements all the customized behavior that Rake::ExtensionTask config had
• Upgrade rb-sys and rb-sys-build crates to version 0.9.94.

These changes streamline the CI configuration, improve cross-platform compatibility, and ensure the project is using the latest rb-sys features. By leveraging the built-in functionality of rb-sys, the project's build and release processes become more efficient and maintainable.

[ankane]

Hi @ianks, thanks for the PR. However, I'd prefer to keep the current approach for now.