Add cloud.availability_zone into azure module

[kaiyan-sheng]

As a part of inventory schema work, we want to make sure aws, azure and googlecloud module all have cloud.availability_zone field. This issue is to track the work for adding cloud.availability_zone into azure module.

[elasticmachine]

Pinging @elastic/integrations-platforms (Team:Platforms)

[kaiyan-sheng]

@narph mentioned to me about we have some issue collecting az for Azure because the zone is not mapped in the sdk although it is returned by the API. We can leave cloud.availability_zone as optional for now.

[narph]

The GetById resource API does return the zone but it looks like it is not mapped inside the Azure SDK.
Someone has already raised this issue Azure/azure-rest-api-specs#3358 for the vm scalesets , will raise an issue as well.

[ravikesarwani]

Closing as stale. No users ask.