Upgrade path from Hub and Spoke to VWAN

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### Description

We have a few customers that have deployed ALZ using hub and spoke and are now wanting to upgrade to VWAN. There is the upgrade path https://learn.microsoft.com/en-us/azure/virtual-wan/migrate-from-hub-spoke-topology but this is just the steps it would be good to know how to do this within ALZ using IaC

#### Is your feature request related to a problem?

hard to understand how to do upgrade via IaC

#### Describe the solution you'd like

Clear documentation on how to upgrade to VWAN using IaC and the ALZ module

#### Additional context