[9.2] (backport #10906) fix(bk): serverless-beats-tests start failing after merging #10734

[mergify]

What does this PR do?

Restore the previous environmental context for the serverless-beats-tests
Run serverless-beats-tests if touching some of the core files.

Why is it important?

Regression, and help with early detection

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

How to test this PR locally

NA

Only in the CI

This PR triggered:

• https://buildkite.com/elastic/beats-agent-serverless-tests/builds/1293

Related issues

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

---

This is an automatic backport of pull request #10906 done by [Mergify](https://mergify.com).

[elasticmachine]

⏳ Build in-progress, with failures

• Buildkite Build
• Commit: a6b1f51

Failed CI Steps

• fips:arm64:sudo-true:fleet
• fips:arm64:sudo-true:fleet

cc @v1v