[8.x](backport #6801) [e2e] Add tests for self monitoring agent logs in otel mode

[mergify]

What does this PR do?

It adds tests for comparing docs ingested by agent.monitoring vs otel.yml

Notes:
Some changes made to otel.yml produced by hand here:

Checklist

• I have read and understood the pull request guidelines of this project.
• 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/fragments using the changelog tool
• I have added an integration test or an E2E test

How to test this PR locally

Related issues

• Closes #4877

---

This is an automatic backport of pull request #6801 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 931134f has failed:

On branch mergify/bp/8.x/pr-6801
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 931134f3f.
  (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:
	modified:   testing/integration/otel_test.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   testing/integration/beat_receivers_test.go

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

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarQube

[mergify]

This pull request has not been merged yet. Could you please review and merge it @khushijain21? 🙏

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: a9668d0

Failed CI Steps

• Win2025:sudo:default
• x86_64:sudo: fqdn

History

• 💔 Build #18987 failed e391c98

cc @khushijain21