Make hostmetricsreceiver available in Agent running in OTel mode

[ycombinator]

What does this PR do?

This PR makes the hostmetrics receiver available to users running Elastic Agent in otel mode.

Why is it important?

To allow users of Elastic Agent running as as OpenTelemetry Collector to configure pipelines containing the hostmetricsreceiver.

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/fragments using the changelog tool
• I have added an integration test or an E2E test

[mergify]

This pull request does not have a backport label. Could you fix it @ycombinator? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[elasticmachine]

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

[ycombinator]

Serverless tests are failing in CI with the following error:

>>> (windows-amd64-2022-fleet) Test output (sudo) (stdout): Error: error starting service: failed to start service (Elastic Agent): The service did not respond to the start or control request in a timely fashion.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
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 otel-mode-add-hostmetrics-receiver upstream/otel-mode-add-hostmetrics-receiver
git merge upstream/main
git push upstream otel-mode-add-hostmetrics-receiver

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[ycombinator]

@strawgate This PR — and therefore the hostmetricsreceiver is not going to make it into 8.14 given that the final BC is being cut tomorrow and there are still CI errors that need investigating.

We did get the elasticsearchexporter and filterprocessor into 8.14 though. Will keep working on getting hostmetricsreceiver and resourcedetectionprocessor into the next release.