[Hybrid Nodes] Remove strict requirement of providing a VGW or TGW during cluster creation

[TiberiuGC]

Description

At the moment, the field remoteNetworkConfig.vpcGatewayID is required when relying on eksctl to create a VPC for you. Removing this requirement comes with the advantage that users no longer need to provide a pre-existing VPC if their hybrid nodes connectivity method does not involve a TGW or VGW. Instead, eksctl will create the VPC for them, with recommended SG rules in place (for hybrid nodes), but no other additional networking pre-requisites (for hybrid nodes).

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the userdocs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes
• (Core team) Added labels for change area (e.g. area/nodegroup) and kind (e.g. kind/improvement)

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[bryantbiggs]

Makes sense!