feat(vm): hotplug cpu (phase 1)

[diafour]

Description

• Change cpu cores setting from domain.resources/limits to domain.cpu fields.
• Support old VMs to not require reboot on module update.

Why do we need it, and what problem does it solve?

It is a phase 1 of implementation of the CPU hotplug support.

Limitations:

• No additional VMClass settings, only spec.cpu.cores in the VM is supported for now.
• Should be explicitly enabled via specifying a featureGate in the ModuleConfig.

Main difference from original Kubevirt:

• Dynamic cores, static sockets count: 1-16 cores 1 socket, 18-32 cores 2 sockets, etc.
• CPU cores reducing is allowed.
• Main Pod and target Pod always have resources.limits for CPU.

What is the expected result?

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: vm
type: feature
summary: "Simple implementation of CPU hotplug"