[8.x] ci: fix benchmarks cleanup (backport #14334)

[mergify]

Motivation/summary

The benchmarks workflow does not clean up all the resources it's creating.

In this workflow run you can see that the Spin up benchmark environment step creates 22 resources.

But the Teardown benchmark environment only deletes 9 resources.

The reason for it is the differently passed TF_VAR_* environment variables in both steps.

This change fixes it and aligns the passed tf vars to both apply and destroy.

Checklist

• Update CHANGELOG.asciidoc
• Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

I was able to test this change in https://github.com/elastic/apm-server/actions/runs/11277362803/job/31363323001, where you can find 22 resources being destroyed.

Related issues

---

This is an automatic backport of pull request #14334 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 9499f3d has failed:

On branch mergify/bp/8.x/pr-14334
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 9499f3dea.
  (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:   .github/workflows/benchmarks.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

[1pkg]

@reakaleek I think the original mistake on my end was to not backport this PR #14245 properly, that's why we now think all the conflicts when backporting CI changes. I reoppened it and will properly backport it now, so we don't need to deal with conflicts in CI.

[mergify]

This pull request is now in conflicts. Could you fix it @mergify[bot]? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/8.x/pr-14334 upstream/mergify/bp/8.x/pr-14334
git merge upstream/8.x
git push upstream mergify/bp/8.x/pr-14334

[1pkg]

@reakaleek I merged CI changes backport to 8.x, and rebased this backport so everything looks sane now. The merge conflict problem should no longer appear in the future. Sorry for the initial conflusion.