Set up tmt test plans and Testing Farm integration

[miabbott]

Integrate tmt (Test Management Tool) and Testing Farm for test orchestration across multiple platforms and Fedora versions.

Tasks

• Create plans/ directory with tmt test plans
• Create .fmf/version file to enable FMF
• Add FMF metadata to tests
• Create GitHub Actions workflow for Testing Farm integration
• Test on multiple Fedora versions (42, 43, Rawhide) and architectures (x86_64, aarch64)

Acceptance Criteria

• tmt run executes tests locally
• Testing Farm runs tests on PRs
• Test results visible in GitHub PR checks

Dependencies

• Depends on Create unit tests for pkg/tar-diff package #35 (pkg/tar-diff tests)
• Depends on Create unit tests for pkg/tar-patch package #36 (pkg/tar-patch tests)
• Depends on Create unit tests for pkg/common package #37 (pkg/common tests)