Introduce VirtualizationProfile CRD to contain details about the virtualization stack

[harshitgupta1337]

Introduce VirtualizationProfile field in the KubevirtConfiguration CRD that captures the specifics of the backend virtualization stack to be used in the plugin virt-launcher.

What this PR does

Before this PR: Several configuration values relating to Libvirt and QEMU were hardcoded in the virt-controller and virt-handler components.

After this PR: All virtualization-stack-related configuration have been moved to a new field in KubevirtConfiguration named VirtualizationProfile. The virt-controller and virt-handler components refer to this field to determine the values for specific fields pertaining to the virtualization stack.

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR.
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