tinyxml2: add xmldoctest and xmlprintertest fuzzers covering XMLDocument API and XMLPrinter

[SomnathDas]

Changes ::

The existing xmlfuzz target only exercises XMLDocument::Parse. Per the Introspector report dated 2026-06-16, the entire XMLPrinter class and a large portion of the XMLDocument API had 0% coverage.

xmlprintertest covers the full XMLPrinter surface: the streaming builder API (OpenElement, CloseElement, all PushAttribute and PushText typed overloads, PushComment, PushDeclaration, PushUnknown, PushHeader, ClearBuffer), the visitor dispatch path triggered via doc.Accept(), and the internal helpers PrintString, PrintSpace, and SealElementIfJustOpened which are reached transitively.

xmldoctest covers the XMLDocument construction and query API: all typed QueryValue and QueryText attribute/text conversion functions, all typed SetAttribute and SetText overloads, the full tree mutation API (New* factory methods, Insert*/DeleteChild/DeleteAttribute), document-level operations (DeepCopy, SaveFile, Clear), the ShallowClone/ShallowEqual/DeepClone paths, XMLHandle and XMLConstHandle traversal, and so on.

Before ::

After ::

Locally ran for about --seconds 180.

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[github-actions]

SomnathDas is a new contributor to projects/tinyxml2. The PR must be approved by known contributors before it can be merged. The past contributors are: arthurscchan, hunsche, vitaliset, kiddo-pwn, DonggeLiu, inferno-chromium, Dor1s, Androbin (unverified), jumde (unverified)