bk: sparse checkout for loading bk pipelines

[v1v]

see elastic/kibana#265568

Release notes

[rn:skip]

What does this PR do?

Check out faster when running the loading bk pipeline defined in the catalog-info

Why is it important/What is the impact to the user?

Checklist

• 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 (and/or docker env variables)
• I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

How to test this PR locally

Related issues

see elastic/kibana#265568
elastic/elastic-agent#12082

Use cases

Screenshots

Logs

[github-actions]

🤖 GitHub comments

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[mergify]

This pull request does not have a backport label. Could you fix it @v1v? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• If no backport is necessary, please add the backport-skip label