Add flow_timeout_in_minutes to VNETs.

[SteffenBoThomsen]

Problem

When either using a Firewall in a brown field deployment or deploying a firewall through SDAF in a green field deployment. It's important to set the VNET flow timeout in accordance with the Firewall idle timeout.

As the idle timeout can be increased only by request to Microsoft support, we can't infer the actual value to set and should therefore delegate to the users.

Furthermore, when having a firewall not controlled by SDAF, it should be possible to disable route propagation on route tables manually.

Solution

Add the option to specify *_flow_timeout_in_minutes for management and workload zone VNETs, defaults to null.
Add the option to specify network_enable_route_propagation for subnet route tables, defaults to true.

[hdamecharla]

Approved