Make TGW creation optional

[goopilot]

Many companies have existing environment with TGW as a core. It would be beneficial to make creation of TGW optional and add parameters to specify existing TransitGateway, TransitGatewayAttachment, TransitGatewayRouteTable etc that could be passed to lambda.

[goopilot]

Any updates on this?

[NickB118]

I think this would be a good idea too