Add additional VPC Infrastructure validation

[cjschaef]

Describe the solution you'd like
[A clear and concise description of what you want to happen.]
Validation of the extended (v2) VPC Infrastructure support should be added in the VPCCluster webhook logic.

This currently includes (but isn't limited to):

• VPC Custom Image definitions

[Karthik-K-N]

Based on the slack conversation moving it to next milestone