Add changelog entry for improved version consistency checks

[mbg]

Adds a changelog entry for #3099 and #3100. Since those have similar objectives, I figured it would make sense to add a combined entry for the two.

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.

[Copilot]

Pull Request Overview

This PR adds a changelog entry documenting improvements to version consistency checks in the CodeQL Action. The changes help prevent users from mixing different versions of the CodeQL Action within the same workflow, which is unsupported and can cause unpredictable results.

Key changes:

• Adds a comprehensive changelog entry combining related PRs #3099 and #3100
• Documents new warning for version mismatches in workflow files
• Documents new error handling for configuration files generated by different versions