Add test for handling processing errors while publishing events

[rdner]

There were some instances of this code producing infinite loops. Now there is a test case for the processing pipeline covering this.

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
  - [ ] I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

How to test this PR locally

cd ./libbeat/publisher/pipeline
go test -run '.*TestClient.*/.*infinite.*'

Related issues

• Relates Processor errors can cause the Beat pipeline to enter what appears to be an infinite loop #34792

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2023-12-22T16:12:13.996+0000

• Duration: 142 min 53 sec

Test stats 🧪

Test	Results
Failed	0
Passed	28734
Skipped	2015
Total	30749

💚 Flaky test report

Tests succeeded.

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