Prepare azure-ai-evaluation release 1.11.0

[slister1001]

Description

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• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
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Testing Guidelines

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[Copilot]

Pull Request Overview

This PR prepares the azure-ai-evaluation package for the 1.11.0 release by finalizing the changelog with the official release date and moving features from "Unreleased" status to the official release section.

Key changes:

• Sets official release date as September 2, 2025 for version 1.11.0
• Consolidates changelog structure by removing "Unreleased" status and empty sections
• Moves new features to the finalized release section