Apply updates to 2025.06 compatibility layer (lmod, ca-certificates, modules) - #239

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@93ea575cb5d8a053eaa0ac8fa3b40d7e05a33cc8, actions/setup-python@v5. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: prefix_required_space)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: gentoo_git_branch)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: gentoo_git_repo)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: compat_defaults_dir)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: gentoo_prefix_path)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: cvmfs_repository)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: custom_overlays)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: eessi_host_arch)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: eessi_host_os)

Variables names from within roles should use compatibility_layer_ as a prefix. (vars: eessi_version)