[8.19](backport #47942) feat: add add_kubernetes_metadata processor to OTel Beat processor

[mergify]

Proposed commit message

Add add_kubernetes_metadata processor to the OTel Beat processor.

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

1. Include the processor in Elastic Agent by adding it to https://github.com/elastic/elastic-agent/blob/89e0e9a5b0ebb376773de813a1fd2c0b2f30e74a/internal/pkg/otel/components.go.
2. Build the Elastic Agent Docker container
3. Run the Agent in Kubernetes with an OTel config that includes the Beat processor.

Example OTel config:

    service:
      pipelines:
        logs:
          receivers:
            - filebeatreceiver
          processors:
            - beat
          exporters:
            - debug

    receivers:
      filebeatreceiver:
        filebeat:
          inputs:
            - type: filestream
              id: var-lib-docker-containers
              paths:
                - /var/lib/docker/containers/*/*.log
        # Clear the list of default processors
        processors: []
        output:
          otelconsumer:
        path.data: /tmp/1205/data
        path.logs: /tmp/1205/logs
        queue.mem:
          flush.timeout: 0

    processors:
      beat:
        processors:
          - add_kubernetes_metadata:
              add_resource_metadata:
                node:
                  enabled: false
              indexers:
                - container:
              matchers:
                - logs_path:

    exporters:
      debug:
        sending_queue:
          enabled: false
        use_internal_logger: false
        verbosity: normal
```<hr>This is an automatic backport of pull request #47942 done by [Mergify](https://mergify.com).

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