[receiver/k8scluster] Add Node resource attributes

[povilasv]

Description:

Add optional k8s.kubelet.version, k8s.kubeproxy.version node resource attributes

Doing some actual testing with kind with k8s_cluster receiver and prometheus exporters.

     k8s_cluster:                                                    
        node_conditions_to_report: [Ready, MemoryPressure]            
        allocatable_types_to_report: [cpu, memory]                    
        resource_attributes:                                                                      
          k8s.kubelet.version:
            enabled: true 
          k8s.kubeproxy.version:                                      
            enabled: true   

and prometheus exporter:

   prometheus:
        resource_to_telemetry_conversion:
          enabled: true
        endpoint: 0.0.0.0:9090

Example metric:

k8s_node_allocatable_cpu{k8s_kubelet_version="v1.25.3",k8s_kubeproxy_version="v1.25.3",k8s_node_name="kind-control-plane",k8s_node_uid="09b55a47-87cb-4790-8834-2341d683999d",opencensus_resourcetype="k8s"} 8

Link to tracking Issue:
#24835

Testing:

• added unit tests
• manua ltest with kind

Documentation:

• generated

[TylerHelmuth]

Will these be added to all metrics or only node metrics?

[povilasv]

Only node metrics, I think it's same as other resource attributes are added only to the relevant metrics.

Example:

resource_attributes:
  k8s.hpa.name:
    description: The k8s hpa name.
    type: string
    enabled: true
  k8s.job.name:
    description: The k8s pod name.
    type: string
    enabled: true

[dmitryax]

Nit: unrelated removal. We usually keep a space here

[povilasv]

Fixed. Thanks for review!