Use the PKI REST API wherever possible instead of XML
    
    The XML API is already deprecated and will be removed in some
    future release.
    
    All but the updateCRL API has an equivalent in REST. The upstream
    dogtag project documents most of the API at
    https://github.com/dogtagpki/pki/wiki/REST-API . I say most
    because not every API includes sample input/output. The
    pki ca-cert command is a good substitute for seeing how the API
    is used by their own tooling.
    
    This changes no pre-existing conventions. All serial numbers are
    converted to decimal prior to transmission and are treated as
    strings to avoid previous limitations with sizing (which would
    have been exacerbated by random serial numbers).
    
    Fixes: https://pagure.io/freeipa/issue/9345
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>