Make elasticinframetricsprocessor available in otel mode

[AlexanderWert]

Describe the enhancement:

Include the elasticinframetricsprocessor in the OTel Collector components we bundle with Elastic Agent.

Describe a specific use case for the enhancement or feature:

Users of Elastic Agent in OTel mode (elastic-agent otel ...) would like to be able to use the elasticinframetricsprocessor in their OTel Collector pipeline configurations to transform infra metrics to corresponding Elastic metrics.

What is the definition of done?

• A test that runs Elastic Agent in OTel mode (elastic-agent otel ...) includes the elasticinframetricsprocessor in it's test OTel Collector configuration and the test passes.

[elasticmachine]

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