Updates to the API for VPC GA (#913)

* updates to the API for vpc GA

* small tweaks to deal with linter issue

* Revert AccountAvailability > unavailable property back to type: list

* Updates AccountAvailability > unavailble property to correctly be an array of strings instead of a list

* Revert /networking/ips/share endpoint back to a v4beta url as per feedback

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Co-authored-by: Matthew Wildman <[email protected]>

Author: Vernholio