virt-api: Apply defaults to VM returned by expand-spec

[lyarwood]

/area instancetype

What this PR does

Before this PR:

Previously the VM returned by the expand-spec subresource API would only expand any referenced instance types and preferences.

After this PR:

This change now applies defaults to the VM and more importantly the VMI spec within to provide a more complete representation of the eventual VMI created from the VM.

Fixes #

Why we need it and why it was done in this way

The following tradeoffs were made:

The following alternatives were considered:

Links to places where the discussion took place:

Special notes for your reviewer

Checklist

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Approvers are expected to review this list.

• Design: A design document was considered and is present (link) or not required
• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Testing: New code requires new unit tests. New features and bug fixes require at least on e2e test
• Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature / API change.
• Community: Announcement to kubevirt-dev was considered

Release note

The `expand-spec` subresource API now applies defaults to the returned `VirtualMachine` to ensure the `VirtualMachineInstanceSpec` within is closer to the eventual version used when starting the original `VirtualMachine`.

[kubevirt-bot]

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[kubevirt-bot]

@lyarwood: 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-kubevirt-e2e-k8s-1.30-sig-operator	6e56ef0	link	true	/test pull-kubevirt-e2e-k8s-1.30-sig-operator

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/test-infra repository. I understand the commands that are listed here.

[lyarwood]

/hold