Add unused Network Firewall with NAT Gateway check

[rajlearner17]

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

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[github-actions]

'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]

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