[Blog post] Breaking down complexity with parent-child and multi-project pipelines

Closes #12830 (closed)

The goal of this blog post is to describe how multi-project and parent-child pipelines features can be leveraged as we tackle growing complexity in software.

TODO:

• Write conclusion section.
• Resolve and remove any TODOs in the draft.
• Verify YAML configurations in the article.
• Add screenshots of pipelines.
• Find cover image or ask designers to create one.
• Review post metadata.

Checklist for writer

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• If time sensitive
  • Added ~"priority" label
  • Mentioned @vsilverthorne to give her a heads up ASAP
• Blog post file formatted correctly, including any accompanying images
• All relevant frontmatter included
• Review app checked for any formatting issues
• Reviewed by fellow team member
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  • Any required internal or external approval for this blog post has been granted (please leave a comment with details)
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