feat: added code scanning through CodeQL

[mohamedzeidan2021]

Issue #, if available:

Description of changes:
CodeQL is a tool directly integrated within GitHub that will try and find vulnerabilities within our code. Once enabled, the file being merged will set up the job, run the tool, and post the vulnerability findings for the team to look at.

Testing done:
Ensured it ran correctly within my fork, and reviewed the vulnerabilities found.

Merge Checklist

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General

• [ x] I have read the CONTRIBUTING doc
• [ x] I certify that the changes I am introducing will be backward compatible, and I have discussed concerns about this, if any, with the Python SDK team
• [ x] I used the commit message format described in CONTRIBUTING
• I have passed the region in to all S3 and STS clients that I've initialized as part of this change.
• I have updated any necessary documentation, including READMEs and API docs (if appropriate)

Tests

• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added unit and/or integration tests as appropriate to ensure backward compatibility of the changes
• I have checked that my tests are not configured for a specific region or account (if appropriate)
• I have used unique_name_from_base to create resource names in integ tests (if appropriate)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.