Refactor validation logic around checking for multiple options

[justinsb]

We also have to move some of the EnvVar handling around to avoid a circular reference.

[justinsb]

WIP because I want to validate that this detects that the json names aren't yet right in v1alpha3 (also I need to rebase for kindnet)

[justinsb]

/retest

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hakman

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [hakman]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-triage-robot]

The Kubernetes project has merge-blocking tests that are currently too flaky to consistently pass.

This bot retests PRs for certain kubernetes repos according to the following rules:

• The PR does have any do-not-merge/* labels
• The PR does not have the needs-ok-to-test label
• The PR is mergeable (does not have a needs-rebase label)
• The PR is approved (has cncf-cla: yes, lgtm, approved labels)
• The PR is failing tests required for merge

You can:

• Review the full test history for this PR
• Prevent this bot from retesting with /lgtm cancel or /hold
• Help make our tests less flaky by following our Flaky Tests Guide

/retest

[k8s-ci-robot]

@justinsb: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-kops-e2e-k8s-gce-ipalias	5fa9690	link	unknown	/test pull-kops-e2e-k8s-gce-ipalias

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.