[Task] Cost reduction for basic and zone-redundant configurations

### Description

The template should only deploy the minimal required resources in the secondary region if regional failover is not needed (basic and zone redundant configurations).

Secondary region networking like vnet and subnets are required in geographies with multi-region support. NSGs should be in place if vnet and subnet are created. Most of these are free / very little cost.

Cost optimization:
- Conditionally create secondary private endpoints and
- Conditionally create NAT Gateway only if regional failover is needed

Ideally same conditional flag could be used for other failover resources in the future

### Definition of Done

```markdown
- Only minimal resources are deployed to secondary region
- Expensive or resources which are not needed for basic | zone-redundant configurations can be conditionally excluded.
- BCDR documentation is updated
```

### Values Provided

- Reduced cost for the overall infrastructure

Start by inspecting the Terraform resource definitions for secondary-region networking, private endpoints, NAT Gateway, and other failover resources, then review the BCDR documentation. Identify the configuration flag for regional failover and verify which resources are required for basic and zone-redundant deployments. Done means unnecessary expensive resources are excluded and the BCDR documentation reflects the behavior.

Written by the indexing model from the issue text.