utils: move parse_cert_verify_opts() into separate file
    
    parse_cert_verify_opts() is only used by p11_child, so it makes sense to
    move the sources nearer together. The related test is still in
    test_utils but it can be split out as well if there are more p11_child
    related unit tests.
    
    Related to https://pagure.io/SSSD/sssd/issue/4032
    
    Reviewed-by: Alexey Tikhonov <atikhono@redhat.com>
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>