Feat/label driven yurtnode conversion (#2533)

• refactor(yurtadm/yurthub): extract reusable host lifecycle helpers for yurthub systemd deployment

• refactor(kubelet): unify traffic redirection helpers for yurthub conversion and revert

• Revert “refactor(kubelet): unify traffic redirection helpers for yurthub conversion and revert”

This reverts commit 94cef5ae2775f4a0d58cfd9f3f768d5fb63e75c3.

• feat(node-servant): switch convert and revert to systemd-based yurthub lifecycle

• refactor(node-servant): unify conversion job rendering for controller-driven workflow

• feat(yurt-manager): add YurtNodeConversionController for label-driven yurthub lifecycle

• feat(yurt-manager): restart node workloads after conversion and protect is-edge-worker label

• fix(nodepool): enqueue old pool when nodepool label is removed

• docs: add comments for yurt node conversion flow

• refactor(node-servant): embed yurthub in image and remove download flags

• refactor(yurtnodeconversion): restart workloads from node-servant job

• fix(node-servant): crictl ps warning pollution

• fix(yurtnodeconversion): keep failed nodes cordoned and avoid mutating cached objects

• test(e2e): migrate yurthub conversion coverage to label-driven controller workflow

• refactor(node-servant): reduce complexity in conversion and runtime helpers

• refactor(node-servant): simplify convert options for edge-only flow

• refactor(yurt-node-conversion): ruduce func Reconcile complexity)

• feat(yurt-node-conversion): skip non-edge nodepool node convert

• refactor(yurt-node-conversion): optimize stale job cleanup and e2e health check