[9.2](backport #47873) cleanup(otel): move otelbeat packages to x-pack/otel

[mergify]

Proposed commit message

Move the remaining otelbeat packages to x-pack/otel so that all otel-related code is centralized.

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.

How to test this PR locally

cd x-pack/filebeat
mage goIntegTest

cd x-pack/metricbeat
mage goIntegTest

Related issues

• Relates otel: update integration tests to use an in-process testing collector #47338
• Relates otel: fix remaining tests to use in process testing collector #47772
• Relates chore(otel): remove otelbeat #47804
• Closes https://github.com/elastic/ingest-dev/issues/6207

  ---

  This is an automatic backport of pull request cleanup(otel): move otelbeat packages to x-pack/otel #47873 done by Mergify.

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