HAPI FHIR: XXE in XsltUtilities.saxonTransform via unhardened Saxon TransformerFactory

Summary org.hl7.fhir.utilities.XsltUtilities exposes two parallel families of XSLT transform helpers. The transform... overloads obtain their TransformerFactory from the project's hardened helper XMLUtil.newXXEProtectedTransformerFactory which sets ACCESSEXTERNALDTD="" and...