Support disabling global metadata processors per output

[cmacknz]

• Relates Add a feature flag to disable injecting the default beat global processors when using the otel runtime #12267
• Relates feat: allow specifying global OTel processors in Agent outputs #12945

#12945 added the ability to configure per output global processors, while #12267 added the ability to globally disable the default add_x_metadata processors.

We should additionally allow disabling the default global processors per output, and simplify the configuration to allow disabling only specific global processors as a convenience. Users who want to directly configure the global processors can disable them and re-add them as global processors.

One major advantage of adding the ability to disable global processors per output is this feature will immediately become available to Fleet users via advanced YAML parameters while we build a proper UI for this.

The default processors feature flag should be extended to support entries per global add_x_metadata processor:

   agent.features:
      default_processors:
        enabled: true # when false disables all default processors everywhere
        add_host_metadata: false # Disable add_host_metadata everywhere
        add_cloud_metadata: false # Disable add_cloud_metadata everywhere
        add_docker_metadata: false # Disable add_docker_metadata everywhere
        add_kubernetes_metadata: false # add_kubernetes_metadata everywhere

The default_processors block should be additionally be supported in each output in addition to the global option:

outputs:
  default:
    type: elasticsearch
    hosts:
      - localhost:9200
    username: elastic
    password: [REDACTED]
    default_processors: # NEW
      enabled: true # when false disables all default processors everywhere
      add_host_metadata: false # Disable add_host_metadata everywhere
      add_cloud_metadata: false # Disable add_cloud_metadata everywhere
      add_docker_metadata: false # Disable add_docker_metadata everywhere
      add_kubernetes_metadata: false # add_kubernetes_metadata everywhere

[infra-vault-gh-plugin-prod]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[infra-vault-gh-plugin-prod]

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

[cmacknz]

The ability to disable all global processors is already part of otel configuration translation and we just need to generalize it a little bit.

elastic-agent/internal/pkg/otel/translate/otelconfig.go

Lines 834 to 839 in 867f7de

	// Strip per-input copies of default processors already run by the beatprocessor.
	if features.DefaultProcessors() {
	if _, ok := input["processors"]; ok {
	input["processors"] = stripDefaultProcessors(comp.BeatName(), input["processors"])
	}
	}

[cmacknz]

I have this mostly implemented, can hopefully get it into review soon.