feat(opentelemetry-collector): add KEDA support

[boqu]

Summary

• Add a keda.enabled values option that omits the replicas field from Deployment and StatefulSet specs, allowing KEDA ScaledObject resources to manage replica counts externally
• Add mutual exclusivity validation between autoscaling.enabled and keda.enabled in _helpers.tpl
• Add CI test values for both deployment and statefulset modes with KEDA enabled
• Bump chart version to 0.146.0

Test plan

• Verify helm template with keda.enabled: true omits replicas from Deployment
• Verify helm template with keda.enabled: true omits replicas from StatefulSet
• Verify helm template fails when both autoscaling.enabled and keda.enabled are true
• Verify CI tests pass with the new keda-deployment-values.yaml and keda-statefulset-values.yaml

[boqu]

This PR is superseded by #2097