feat: Update kernel matrix with Cloud Hypervisor

[Callisto13]

This is fairly simple to do now that the modules are mounted in separately.

Here I have restructured the kernel directory to build both firecracker and cloud-hypervisor images. Whichever you are using, the CAPMVM root image will be the same as there is no connection anymore.

kernel/
├── bin
│   └── Dockerfile
├── builder
│   └── Dockerfile
├── cloud-hypervisor
│   ├── base
│   │   └── Dockerfile
│   └── configs
│       └── linux-x86_64-5.12.config
├── firecracker
│   ├── base
│   │   └── Dockerfile
│   └── configs
│       ├── linux-x86_64-4.19.215.config
│       └── linux-x86_64-5.10.77.config
├── Makefile
├── modules
│   └── Dockerfile
└── README.md

The readme has been updated to describe the sequence and how images relate to each other.

Tested against the CH pr in flintlock with this hammertime spec:

{
    "id": "mvm1",
    "namespace": "ns1",
    "vcpu": 2,
    "memory_in_mb": 2048,
    "kernel": {
      "image": "docker.io/claudiaberesford/cloudhypervisor-kernel-bin:5.12",
      "filename": "boot/vmlinux.bin",
      "add_network_config": true
    },
    "root_volume": {
      "id": "root",
      "is_read_only": false,
      "source": {
        "container_source": "docker.io/claudiaberesford/capmvm-k8s-os:1.23.5"
      }
    },
    "additional_volumes": [
      {
        "id": "modules",
        "is_read_only": false,
        "source": {
          "container_source": "docker.io/claudiaberesford/cloudhypervisor-kernel-modules:5.12"
        },
        "mount_point": "/lib/modules/5.10.77"
      }
    ],
    "interfaces": [
      {
        "device_id": "eth1",
        "guest_mac": "7e:f5:45:49:38:e0",
        "type": 0
      }
    ],
    "metadata": {
      "meta-data": "aW5zdGFuY2VfaWQ6IG5zMS9tdm0wCmxvY2FsX2hvc3RuYW1lOiBtdm0wCnBsYXRmb3JtOiBsaXF1aWRfbWV0YWwK",
      "user-data": "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"
    }
}

[Callisto13]

@richardcase this is looking doable with minimal duplication. Will test these images with your PR tomorrow

[yitsushi]

lgtm