feat(collector): add resourceDetection preset for parity with the kube-stack helm chart

[cyrille-leclerc]

Here is the PR description:

---

Add resourceDetection preset to the opentelemetry-collector chart

Goal

Implement the presets.resourceDetection feature in the opentelemetry-collector chart, bringing it to parity with the equivalent preset already present in the opentelemetry-kube-stack chart (see otel-kube-stack PR here).

Implementation

A new presets.resourceDetection block is introduced with a top-level enabled flag (default: false for backward compatibility). When set to true, the chart injects a resourcedetection/env processor into all configured pipelines (logs, metrics, traces).

Supported detectors

Detector	Enabled by default (when resourceDetection.enabled: true)	Purpose
env	✅ yes	Reads resource attributes from environment variables
k8snode	✅ yes	Detects node-level attributes from the Kubernetes API
eks	❌ no	Detects EKS cluster name
aks	❌ no	Detects AKS cluster name
gcp	❌ no	Detects GCP/GKE cluster name

Each detector can be individually overridden regardless of the top-level enabled state.

Sample configuration

presets:
  # ...

  # Configures the collector to detect resource attributes adding a resourcedetection processor named `resourcedetection/env` to the pipelines.
  # Adds the resourcedetection/env processor to all pipelines.
  # Each detector can be enabled individually. Base detectors `env` and `k8snode` are enabled by default when `resourceDetection/enabled` is `true`. 
  # Cloud provider specific detectors (`eks`, `aks`, `gcp`)
  resourceDetection:
    enabled: false
    env:
      enabled: true
    k8snode:
      enabled: true
    eks:
      enabled: false
    aks:
      enabled: false
    gcp:
      enabled: false

Follow-up

A subsequent PR will add presets.resourceDetection to the opentelemetry-kube-stack chart, including the enabled flag and the env/k8snode sub-configs. The only difference from this chart will be that presets.resourceDetection.enabled defaults to true there, since the kube-stack chart already ships resourcedetection/env (with env + k8snode) as part of its default daemon collector configuration.