[Metricbeat] Add container metrics to the Azure module

[sorantis]

Add support of the following namespaces in Azure Monitor that cover container metrics:

Namespace: Microsoft.ContainerInstance/containerGroups
Namespace: Microsoft.ContainerRegistry/registries
Namespace: Microsoft.ContainerService/managedClusters

Reference: https://docs.microsoft.com/en-us/azure/azure-monitor/platform/metrics-supported#microsoftcontainerinstancecontainergroups

Modules

For a metricset to go GA, the following criterias should be met:

• Supported versions are documented
• Supported operating systems are documented (if applicable)
• Integration tests exist
• System tests exist
• Automated checks that all fields are documented
• Documentation
• Fields follow ECS and naming conventions
• Dashboards exists (if applicable)
• Kibana Home Tutorial (if applicable)
  • Open PR against Kibana repo with tutorial. Examples can be found here.
• Example data.json exists and an automated way to generate it exists (go test -data)
• Test environment in Docker exist for integration tests

[narph]

container metricsets have been added together with dashboards and documentation. Can we close this issue @sorantis ?