Cherry-pick #15342 to 7.x: Add azure storage metricset

[narph]

Cherry-pick of PR #15342 to 7.x branch. Original message:

Should handle:
#14548
#14549
#14551
#14552

Configuration:

- module: azure
  metricsets:
  - storage
  enabled: true
  period: 300s
  client_id: '${AZURE_CLIENT_ID:""}'
  client_secret: '${AZURE_CLIENT_SECRET:""}'
  tenant_id: '${AZURE_TENANT_ID:""}'
  subscription_id: '${AZURE_SUBSCRIPTION_ID:""}'
  refresh_list_interval: 600s
  resources:
  - resource_group: [""]
    service_type: ["blob", "file"]
  - resource_id: [""]  

Output:

 {
        "_index" : "metricbeat-8.0.0-2020.01.06-000001",
        "_type" : "_doc",
        "_id" : "JRT4e28BQe78yNOEWjXE",
        "_score" : null,
        "_source" : {
          "@timestamp" : "2020-01-06T17:42:00.000Z",
          "agent" : {
            "type" : "metricbeat",
            "ephemeral_id" : "297967de-3c3a-40eb-a7c6-e7b06fbe774b",
            "hostname" : "DESKTOP-RFOOE09",
            "id" : "297967de-3c3a-40eb-a7c6-e7b06fbe774b",
            "version" : "8.0.0"
          },
          "ecs" : {
            "version" : "1.2.0"
          },
          "host" : {
            "os" : {
              "family" : "windows",
              "name" : "Windows 10 Pro",
              "kernel" : "10.0.18362.535 (WinBuild.160101.0800)",
              "build" : "18362.535",
              "platform" : "windows",
              "version" : "10.0"
            },
            "id" : "297967de-3c3a-40eb-a7c6-e7b06fbe774b",
            "hostname" : "DESKTOP-RFOOE09",
            "architecture" : "x86_64",
            "name" : "DESKTOP-RFOOE09"
          },
          "service" : {
            "type" : "azure"
          },
          "cloud" : {
            "provider" : "azure",
            "region" : "westeurope"
          },
          "event" : {
            "dataset" : "azure.storage",
            "module" : "azure",
            "duration" : 9280652400
          },
          "metricset" : {
            "name" : "storage",
            "period" : 300000
          },
          "azure" : {
            "subscription_id" : "297967de-3c3a-40eb-a7c6-e7b06fbe774b",
            "namespace" : "Microsoft.Storage/storageAccounts",
            "storage" : {
              "successe2elatency" : {
                "avg" : 26.516666666666666
              },
              "availability" : {
                "avg" : 100
              },
              "transactions" : {
                "total" : 310
              },
              "ingress" : {
                "total" : 7723808.0
              },
              "egress" : {
                "total" : 1473483.0
              },
              "successserverlatency" : {
                "avg" : 16.883333333333333
              }
            },
            "resource" : {
              "type" : "Microsoft.Storage/storageAccounts",
              "group" : "obs-infrastructure",
              "name" : "obsdiaglinux"
            }
          }
        },
        "sort" : [
          1578332520000
        ]
      },
      {
        "_index" : "metricbeat-8.0.0-2020.01.06-000001",
        "_type" : "_doc",
        "_id" : "KBT4e28BQe78yNOEWjXE",
        "_score" : null,
        "_source" : {
          "@timestamp" : "2020-01-06T17:42:00.000Z",
          "agent" : {
            "version" : "8.0.0",
            "type" : "metricbeat",
            "ephemeral_id" : "297967de-3c3a-40eb-a7c6-e7b06fbe774b",
            "hostname" : "DESKTOP-RFOOE09",
            "id" : "297967de-3c3a-40eb-a7c6-e7b06fbe774b"
          },
          "service" : {
            "type" : "azure"
          },
          "cloud" : {
            "provider" : "azure",
            "region" : "westeurope"
          },
          "event" : {
            "dataset" : "azure.storage",
            "module" : "azure",
            "duration" : 9281658700
          },
          "metricset" : {
            "name" : "storage",
            "period" : 300000
          },
          "azure" : {
            "subscription_id" : "297967de-3c3a-40eb-a7c6-e7b06fbe774b",
            "namespace" : "Microsoft.Storage/storageAccounts/tableServices",
            "storage" : {
                "successserverlatency" : {
                  "avg" : 115.76666666666667
                },
                "successe2elatency" : {
                  "avg" : 118.63333333333334
                },
                "availability" : {
                  "avg" : 100
                },
                "transactions" : {
                  "total" : 30
                },
                "ingress" : {
                  "total" : 2248122.0
                },
                "egress" : {
                  "total" : 1209276.0
              }
            },
            "resource" : {
              "name" : "obsdiagwin",
              "type" : "Microsoft.Storage/storageAccounts",
              "group" : "obs-infrastructure"
            }
          },
          "ecs" : {
            "version" : "1.2.0"
          },
          "host" : {
            "name" : "DESKTOP-RFOOE09",
            "hostname" : "DESKTOP-RFOOE09",
            "architecture" : "x86_64",
            "os" : {
              "platform" : "windows",
              "version" : "10.0",
              "family" : "windows",
              "name" : "Windows 10 Pro",
              "kernel" : "10.0.18362.535 (WinBuild.160101.0800)",
              "build" : "18362.535"
            },
            "id" : "297967de-3c3a-40eb-a7c6-e7b06fbe774b"
          }
        },
        "sort" : [
          1578332520000
        ]
      },

PR also contains:

• fix on generated fields and modified dashboard
• change on the way metric values are retrieved and events are sent. The events are sent now after all metric values are retrieved for each resource. In the past, events were sent only after all metric value calls are returned for all resources in the config (this took some time if the number of resources is larger)

[kaiyan-sheng]

These extra changelog entries need to be removed.

[narph]

that was fast, just updated changelog