[release/v7.4] Add 7.4.12 Changelog

[pwshBot]

This pull request updates the changelog for version 7.4.12, documenting internal improvements, build and packaging updates, and minor corrections for consistency and clarity. The most significant changes are the addition of new release notes, build pipeline updates, and improvements to documentation formatting.

Release notes and build updates:

• Added a new section for version 7.4.12, including CodeQL suppressions and several build and packaging improvements such as updating the .NET SDK to 8.0.413, updating container images, and making logical template names consistent between pipelines.
• Updated third-party library versions to 8.0.19 for ObjectPool, Windows Compatibility, and System.Drawing.Common.

Documentation and formatting improvements:

• Standardized capitalization of "JSON" and "XML" in changelog entries for improved consistency (e.g., "experimental-feature JSON files", "Invoke-WebRequest XML and JSON errors format"). [1] [2]
• Corrected terminology in previous changelog entries, such as changing "json file" to "JSON file".

[TravisEz13]

/azp run PowerShell-CI-linux-packaging, PowerShell-Windows-Packaging-CI

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