[Spike: 2h] Fix storage backups for Azure clusters

[GeorgianaElena]

This is a follow-up to #624 and is blocking #4426

While working on validating that restoring backups works, I couldn't find any backup instances, so we need to figure out what's missing to get that working.

I suspect https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/backup_protected_file_share is the missing bit, but we should verify this

Tasks

• Explore adding https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/backup_protected_file_share to our terraform code and if this results in backups being created

Definition of done

Monitor backup creation in Backup Center -> Backup instances of the the Azure Portal. Either:

• new backups are being created and the issue is resolved, or;
• backups are not being created and further spikes are required.

[sgibson91]

I tried to add the suggested terraform resources but with no luck. Details of my experiment can be found in #4627

Eventually, I tried configuring the backups manually in Azure Portal, to see if I could figure out why the file share wasn't being discovered. It turns out that NFS shares are not supported for backup! So our terraform config will never work! https://werecomputersamistake.com/