MINIFICPP-2596 Add XMLRecordSetWriter controller service

[lordgamez]

https://issues.apache.org/jira/browse/MINIFICPP-2596

Depends on #1995

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[Copilot]

Pull Request Overview

This PR implements a new XMLRecordSetWriter controller service for Apache NiFi MiNiFi C++, which converts RecordSet data structures to XML format. The writer provides configurable XML output options including root/record tag naming, array element wrapping, XML declaration control, and pretty printing.

Key changes include:

• Implementation of XMLRecordSetWriter controller service with comprehensive property configuration
• Unit test suite covering various XML output scenarios and edge cases
• Documentation updates to include the new controller service

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
XMLRecordSetWriter.h	Header file defining the XMLRecordSetWriter class with properties and enum for array wrapping options
XMLRecordSetWriter.cpp	Implementation of XML conversion logic and property validation
XMLRecordSetWriterTests.cpp	Comprehensive unit tests covering functionality and error conditions
CONTROLLERS.md	Documentation addition for the new XMLRecordSetWriter controller service

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