The controller doesn't generate `%s-generated-kubeletconfig-%s` files for new MCPs

[therealak12]

We have an OKD cluster with approximately 10 MachineConfigPools (MCPs) that inherit from the worker MCP.
When we add a new MCP, the 97 and 98 kubelet configurations are not generated for it.
They are only created after restarting the Machine Config Controller pod.

I suspect this happens because the kubelet config controller does not register any event handlers on the MCP informer. As a result, adding a new MCP does not trigger reconciliation. When the operator is restarted, the FeatureGate informer emits an initial ADD event, which then triggers reconciliation and leads to the generation of the missing kubeletConfigs.

To reproduce the issue, watch the MachineConfigs (oc get machineconfig -w) and apply a new MCP, for example, as shown below.
The expected behavior is that three MachineConfigs are generated: 97-demo-generated-kubelet, 98-demo-generated-kubelet, and rendered-demo-uuid.

In practice, only rendered-demo-uuid is created. The 97 and 98 kubelet MachineConfigs are generated only after the controller pod is restarted.

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfigPool
metadata:
  labels:
    machineconfiguration.openshift.io/role: demo
    pools.operator.machineconfiguration.openshift.io/demo: ""
  name: demo
spec:
  machineConfigSelector:
    matchExpressions:
      - key: machineconfiguration.openshift.io/role
        operator: In
        values:
        - worker
        - demo
  maxUnavailable: 1
  nodeSelector:
    matchLabels:
      node-role.kubernetes.io/demo: ""
  paused: false

[therealak12]

Another possibility is the deadlock explained here:
#3090