Use the inquires to show relevant data for:

• existing AWS VPC => 5 points
• existing GCP VPC => 3 points

More details from duplicate SDA-4706:

in https://gitlab.cee.redhat.com/service/uhc-portal/-/merge_requests/2781 I implemented the basics for validating cloud provider credentials using the inquiries endpoint.

In its current version, it's just validation - it allows the user to advance to the next step when credentials are correct.
This is only a partial implementation of the intended goal of the feature.

AWS regions should come from /api/clusters_mgmt/v1/aws_inquiries/regions
to only show regions available in the account

VPCs should be in a dropdown populated from the aws_inquiries or gcp_inquiries endpoint so the user doesn't have to type their names, same for encryption key names and keyring names for GCP encryption settings.

All of these queries should be using the credentials that are in the form, and can be queried after validation is complete, while keeping in mind that the GCP VPCs / keyring / encryption keys can only be queried after the user selects a region - so they're better suited to query when the user moves to the network screen.