Add unused Network Firewall with NAT Gateway check

[rajlearner17]

Is your feature request related to a problem? Please describe. A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

Reference https://aws.amazon.com/network-firewall/pricing/

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[github-actions[bot]]

'This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 30 days.'

[github-actions[bot]]

'This issue was closed because it has been stalled for 90 days with no activity.'