Azure Firewall snippet res-firewall should be renamed

[StefanIvemo]

Is your feature request related to a problem? Please describe.
Azure Firewall snippet res-firewall is using classic rules. Classic rules is beeing replaced by Azure Firewall Policy which is now the recommended way of deploying Azure Firewall. https://docs.microsoft.com/en-us/azure/firewall-manager/policy-overview#classic-rules-and-policies

Describe the solution you'd like
The declaration in res-firewall is still supported, but it should be highlighted that it's using classic rules. I suggest renaming the the snippet to res-firewall-classic-rules.