feat: add nat_gateway_private_ips output @johncblandii (#229)
## what- Add
nat_gateway_private_ipsoutput to expose private IP addresses of NAT Gateways - Follows the existing pattern used for other NAT Gateway attributes
why
- Users need access to NAT Gateway private IPs for internal networking configurations (e.g., security groups, route debugging)
- Enables use of these IPs as inputs to other components
references
- Requested in feature request: NAT gateway private IPs output support