GitHub cache

[afeefghannam89]

• Add warm_apt_cache.yml. A Dedicated workflow that pre-downloads Elastic apt packages to the GitHub Actions cache (triggered on push to main, nightly, and manually)
• All test workflows restore the apt cache before running molecule. The version-based cache key updates automatically on new Elastic releases
• Add pip caching (actions/setup-python cache: 'pip') to all workflows
• Mount cached packages into molecule Docker containers via read-only volume; copy .deb files into apt archives in prepare.yml