Revise CHANGES.md for upcoming release

[damccorm]

Updated release notes for versioning and added new features, improvements, and bugfixes.

Please add a meaningful description for your change here

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• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
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[gemini-code-assist]

Summary of Changes

Hello @damccorm, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request prepares the CHANGES.md file for future releases by introducing a templated structure for upcoming versions, including a dedicated section for Beam 3.0.0 development highlights and security fixes. It also reorganizes existing release note entries to align with this new, forward-looking format.

Highlights

• Release Note Templating: The CHANGES.md file has been updated to include placeholders for an upcoming 2.XX.X release and a new "Beam 3.0.0 Development Highlights" section.
• Security Fixes Section: A dedicated "Security Fixes" section has been added to the release notes template to clearly delineate security-related updates.
• Content Reorganization: Existing detailed release notes for version 2.71.0 have been moved and re-categorized to fit the new, templated CHANGES.md structure.

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[github-actions]

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[damccorm]

Thanks - fixed both