Fix reconciliation error for empty kubeletConfig with externally set subfields

[jingyih]

Cherry pick the fix in GoogleCloudPlatform/magic-modules#11971.

This resolves the reconciliation error that occurs when kubeletConfig is empty in the user's configuration, but a subfield under kubeletConfig is set externally outside of KCC.

{"severity":"error","timestamp":"2024-10-21T23:33:23.865Z","logger":"containernodepool-controller","msg":"error applying desired state","resource":{"name":"test-b-374795345-10212024-pool","namespace":"default"},"error":"summary: googleapi: Error 400: At least one of ['node_version', 'image_type', 'updated_node_pool', 'locations', 'workload_metadata_config', 'upgrade_settings', 'kubelet_config', 'linux_node_config', 'tags', 'taints', 'labels', 'node_network_config', 'gcfs_config', 'gvnic', 'confidential_nodes', 'logging_config', 'fast_socket', 'resource_labels', 'accelerators', 'windows_node_config', 'machine_type', 'disk_type', 'disk_size_gb', 'storage_pools', 'containerd_config', 'resource_manager_tags', 'performance_monitoring_unit', 'queued_provisioning', 'max_run_duration'] must be specified.\nDetails:\n[\n  {\n    \"@type\": \"type.googleapis.com/google.rpc.RequestInfo\",\n    \"requestId\": \"0x19bb67b615f44eff\"\n  }\n]\n, badRequest"}

Tested locally in b/374795345.

[jingyih]

/cc @maqiuyujoyce @cheftako

[maqiuyujoyce]

/lgtm

Deferring the approval to @cheftako .

[jingyih]

Presubmit / tests-e2e-samples failed with

2024-10-22T16:59:35.0672593Z         --- FAIL: TestAllInSeries/samples/workerpool-with-peered-network (240.48s)

Tested locally the test passed. Will trigger a rerun.

[cheftako]

/lgtm
/approve

[google-oss-prow]

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