feat(aer): Add support for managing vms

[mccormickt]

Adds support for VMs to aer. Validated with my own auraed locally:

» aer vm allocate test-vm \
 --machine-vcpu-count 2 --machine-mem-size-mb 2048 \
--machine-kernel-img-path /var/lib/aurae/vm/kernel/vmlinux.bin \
--machine-root-drive-image-path /var/lib/aurae/vm/image/disk.raw

» aer vm start test-vm
VmServiceStartResponse {
    auraed_address: "[fe80::2%36]:8080",
}

» aer vm list
VmServiceListResponse {
    machines: [
        VirtualMachineSummary {
            id: "test-vm",
            status: "Running",
            mem_size_mb: 2048,
            vcpu_count: 2,
            kernel_img_path: "/var/lib/aurae/vm/kernel/vmlinux.bin",
            root_dir_path: "/var/lib/aurae/vm/image/disk.raw",
            auraed_address: "[fe80::2%36]:8080",
        },
    ],
}

Tweaked our macro as well to allow for repeated arguments to be able to map to repeated protobuf fields.