Support for running OS tests for Debian 12 on arm64

[twz123]

Description

Select the self-hosted ARM runners when building k0s if the architecture is arm or arm64. The k0s build system doesn't support cross-compilation, so the only way to get ARM binaries is to build on ARM. Add the "arch" variable to the ostests Terraform modules. Select the correct default instance type based on the arch. Add arm64 support for Debian 12. Add the arch parameter to the ostests matrix so that it can also run on arm64.

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation update

How Has This Been Tested?

• [x] Manual test
• [ ] Auto test added

Checklist:

• [x] My code follows the style guidelines of this project
• [x] My commit messages are signed-off
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [x] I have checked my code and corrected any misspellings