Issue #8163 : Harden XmlInputStream StAX factory against XXE

[mattcasters]

fixes #8163

XmlInputStream created a raw StAX XMLInputFactory and never disabled DTD processing or external entity resolution. Other Hop XML parsers already go through XmlParserFactoryProducer (DOM/SAX/Schema) or set the two StAX flags locally.

This adds XmlParserFactoryProducer.createSecureXmlInputFactory() (SUPPORT_DTD=false, IS_SUPPORTING_EXTERNAL_ENTITIES=false, best-effort ACCESS_EXTERNAL_DTD/SCHEMA) and uses it from:

• XmlInputStream (the reported sink)
• WebService (SOAP/HTTP responses)
• XmlFormatter
• AdvancedXmlOutput and Excel StaxUtil (already local flags; they now share the helper)

Behavior change: XML documents that contain a DOCTYPE will fail to parse. That is the intended trade-off.

Tests

• Factory property assertions and a canary-file external-entity test in XmlUtilsTest
• XmlInputStreamTest regression that the canary is not emitted as row data

Targeted unit tests: ./mvnw -pl core,plugins/transforms/xml,plugins/transforms/excel,plugins/transforms/webservices -am test -Pskip-uitest

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