Add support for hvi vmm #1133

urunc supports qemu, firecracker, cloud-hypervisor, Solo5 and hyperlight. This issue proposes adding hvi as another monitor for Linux guests.

hvi is a small KVM-based VMM for Linux guests that brings:

• A small footprint: a single static binary for x86-64 and aarch64.
• Visibility at the device boundary: hvi owns guest RAM and the virtio devices, so it can report what the guest does at that boundary.
• A simple device model: every device sits on virtio-mmio, and hvi applies its own seccomp sandbox.
• Built-in agent access: a host socket relayed to the guest's vsock, which urunc exec can use.