feat(operator): support extraObjects

[younsl]

Add extraObjects to the opentelemetry-operator chart, allowing users to deploy additional Kubernetes manifests alongside the operator in a single Helm release.

This is useful for managing custom resources such as Instrumentation or OpenTelemetryCollector directly within the operator chart, without requiring a separate release.

Consistent with the existing pattern in opentelemetry-kube-stack and opentelemetry-target-allocator charts.

Test results

With extraObjects values:

$ helm template test charts/opentelemetry-operator/ \
    --set 'extraObjects[0].apiVersion=v1' \
    --set 'extraObjects[0].kind=ConfigMap' \
    --set 'extraObjects[0].metadata.name=test-extra' \
    --set 'extraObjects[0].data.key=value'
...
kind: ConfigMap
metadata:
  name: test-extra
---

Default (empty extraObjects) renders without errors:

$ helm template test charts/opentelemetry-operator/
---
# Source: opentelemetry-operator/templates/serviceaccount.yaml
apiVersion: v1
...