Add ability to automatically use all labels as dimensions for Prometheus

[TravisStark]

Description

Currently, in the event the application exposes a new label, the customer must explicitly include the new label in "dimensions" and update configuration to make that new label available in CloudWatch Metrics.

This change allows customers to leave dimensions off of metric_declaration and receive all available dimensions.

Current

    {
      "logs": {
        "credentials": {
          "role_arn": "arn..."
        },
        "metrics_collected": {
          "prometheus": {
            "prometheus_config_path": "/etc/prometheusconfig/prometheus.yaml",
            "emf_processor": {
              "metric_declaration": [
                {
                  "source_labels": [
                    "job"
                  ],
                  "label_matcher": "(kubernetes-apiservers|rdi-metric-exporter|kube-state-metrics)",
                  "dimensions": [
                    [
                      "ClusterName",
                      "Service"
                    ]
                  ],
                  "metric_selectors": [
                    ".*"
                  ]
                }
              ]
            }
          }
        },
        "force_flush_interval": 5
      }
    }

New

    {
      "logs": {
        "credentials": {
          "role_arn": "arn:aws:iam::939706305709:role/AWSCloudWatchRoleToBeAssumed"
        },
        "metrics_collected": {
          "prometheus": {
            "prometheus_config_path": "/etc/prometheusconfig/prometheus.yaml",
            "emf_processor": {
              "metric_declaration": [
                {
                  "source_labels": [
                    "job"
                  ],
                  "label_matcher": "(kubernetes-apiservers|rdi-metric-exporter|kube-state-metrics)",
                  "metric_selectors": [
                    ".*"
                  ]
                }
              ]
            }
          }
        },
        "force_flush_interval": 5
      }
    }

Link to tracking issue

Fixes

Testing

Documentation