refactor(runtime): unify workload execution

[MarcStdt]

Summary

• replace backend-facing global/reserved port lists with one resolved port collection
• create one stable Kubernetes Service per logical runtime port
• select every exposing workload through shared port labels
• run each Kubernetes persistent command as one StatefulSet with ordered init containers and one main container
• publish persistent Services before Pod readiness so coldstarter traffic can hand off to the main workload
• stream workload consoles directly from Docker and Kubernetes backends, including init-container logs
• preserve port Services across command and runtime stops while cleaning up legacy workloads

Validation

• go test ./...
• go vet ./internal/runtime/kubernetes
• git diff --check
• rebuilt/imported druid:local into k3d
• verified coldstarter response, wake handoff, Paper 1.21.7 response, and runtime console through public port 11012

[druid-infra]

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