r/(linux|windows)_virtual_machine_scale_set: fixing the parsing of settings and protected_settings when these are empty strings

[tombuildsstuff]

This PR supersedes the work done by @416e64726579 in #8420 - and adds a test to the azurerm_windows_virtual_machine_scale_set resource to capture using a VM Extension where only Settings are configured.

In addition this splits the VM Extension tests out into their own file, since there's enough of them to make this worthwhile.

[jackofallops]

Thanks @tombuildsstuff - LGTM 👍

[tombuildsstuff]

Tests look ok 👍

[ghost]

This has been released in version 2.45.0 of the provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading. As an example:

provider "azurerm" {
    version = "~> 2.45.0"
}
# ... other configuration ...

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 [email protected]. Thanks!