Unify the lazily-initialized statics on std::sync::LazyLock, which the
newer code already uses: the embed_data! macro expands to a plain
static now, which also removes the visibility-forwarding workaround the
lazy_static! matcher forced on it (the @expand arm wrapping vis in
parentheses), and the 'static ref' spelling is kept at the call sites.
distro_info's HTTP client, the apt keyring cache and the new-template
registry follow the same pattern.
vhaudiquet