[8.19](backport #47775) ci: use if_changed

[mergify]

Proposed commit message

• remove dependency on the BK plugin monorepo-diff
• I added the main pipeline to the list of include so it can test the changes too.

Why is it important?

• Faster builds
• Remove the intermediate step to load the monorepo diff step

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
• I have added tests that prove my fix is effective or that my feature works. Where relevant, I have used the stresstest.sh script to run them under stress conditions and race detector to verify their stability.
• I have added an entry in ./changelog/fragments using the changelog tool.

Disruptive User Impact

Author's Checklist

• [ ]

How to test this PR locally

Related issues

Use cases

Screenshots

Logs

---

This is an automatic backport of pull request #47775 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of da79b6e has failed:

On branch mergify/bp/8.19/pr-47775
Your branch is up to date with 'origin/8.19'.

You are currently cherry-picking commit da79b6ecc.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .buildkite/pipeline.yml

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[botelastic]

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