Use package-install for cross platform install

What does this Merge Request do and why?

This MR changes the way 'vale' and 'shellcheck' are installed as they both currently do not offer macOS arm64 binaries via their releases. Instead, we lean on support/dev/package-install to provide the correct package manager to install the necessary packages.

Without this MR, manual installation of shellcheck and vale are currently required on macOS arm64 to allow GDK development.

This also substantially reduces the complexity of the logic to install and run both shellcheck and vale.

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.