[8.6](backport #34870) Add test for the processor re-use issue

[mergify]

This is an automatic backport of pull request #34870 done by Mergify.
Cherry-pick of 3d917c8 has failed:

On branch mergify/bp/8.6/pr-34870
Your branch is up to date with 'origin/8.6'.

You are currently cherry-picking commit 3d917c8519.
  (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)

Changes to be committed:
	new file:   filebeat/channel/runner_mock_test.go
	modified:   filebeat/channel/runner_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   filebeat/channel/runner.go

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

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[elasticmachine]

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• Start Time: 2023-03-21T17:44:58.633+0000

• Duration: 72 min 27 sec

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Test	Results
Failed	0
Passed	7177
Skipped	746
Total	7923

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