iface: support matching against alt-name in copy-mac-from

Resolve the copy-mac-from interface reference through iface_name_search
which already maps alt-names and profile names to kernel names.

Integration test included.

Resolves: https://redhat.atlassian.net/browse/RHEL-145074
Signed-off-by: Jan Vaclav <jvaclav@redhat.com>
Assisted-by: Claude Opus 4.6