fix(ansible): load the shared vars for every inventory

[catinspace-au]

hyperi_github_token, hyperi_github_headers, hyperi_github_env and
hyperi_core_versions lived in inventories/localhost/group_vars, so
playbooks/main.yml only worked with that one inventory. Against any
other, a test VM or a fleet host, the first task to reference them
failed undefined - the Rust role's build-environment step, on a clean
VM, after thirty tasks had run. The variables belong to the playbook,
not to one inventory: they are read from the control node's
environment and name the versions the roles install. Moved to
playbooks/group_vars, which Ansible loads beside the playbook for
whatever inventory is passed. The localhost install path is unchanged.