live_images: additional_repos -> repo
ostree: source_repo_from -> repo_from
extra_source_repos -> repo
ostree_installer: source_repo_from -> repo_from
With the change, the phases have consolidate option names for variant
repos and external repos.
Old option names will continue to work, old names will be converted
to new names after validation automatically if new options are not
specified in config.
Signed-off-by: Qixiang Wan <qwan@redhat.com>
2ae8710934