patch for bigquery unittest with sql_header

[Kayrnt]

Resolves #9775
Based of @takemikami post on fixing SQL header integration in unit tests for BigQuery.

Problem

Solution

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[cla-bot]

Thanks for your pull request, and welcome to our community! We require contributors to sign our Contributor License Agreement and we don't seem to have your signature on file. Check out this article for more information on why we have a CLA.

In order for us to review and merge your code, please submit the Individual Contributor License Agreement form attached above above. If you have questions about the CLA, or if you believe you've received this message in error, please reach out through a comment on this PR.

CLA has not been signed by users: @takemikami

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.82%. Comparing base (300aa09) to head (478cd62).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11386      +/-   ##
==========================================
- Coverage   88.90%   88.82%   -0.08%     
==========================================
  Files         191      191              
  Lines       24391    24394       +3     
==========================================
- Hits        21684    21669      -15     
- Misses       2707     2725      +18     

Flag	Coverage Δ
integration	85.77% <100.00%> (-0.15%)	⬇️
unit	62.81% <20.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Unit Tests	62.81% <20.00%> (-0.01%)	⬇️
Integration Tests	85.77% <100.00%> (-0.15%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[VersusFacit]

@takemikami These commits trace back to a blog post you made. Could you explain the use case behind these lines? After some thoughtful experimentation, I don't see how they are used or what user feature they are enabling. I was able to use the other code in this PR to enable injection of a sql header inside and will have a PR for this soon. However, could you answer what these lines are for? (I tried a few obvious things like {{ tested_node_config }} but this leads to a compiler use before instantiation problem)