Update CodeQL scanning to separate workflow and fix issues

[janechu]

Pull Request

📖 Description

This change moves the CodeQL scan to a separate workflow, adds a workflow dispatch to the platform workflow and fixes a few issues identified by CodeQL.

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

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