M1/M2 Macs 10.15 and up - enable the AppleVZ backend

**What are you trying to do?**
_A description of what you want to happen._

Currently, the only Multipass driver on M1/M2 Macs is QEMU, which is great, but means GUI is limited to X11 forwarding, either on ssh, vnc, or rdp. Adding the virtualbox local.driver option would allow for a localized GUI which could then in theory run Wayland sessions.

**What's your proposed solution?**
_A description of how you think this could be solved, including any alternatives that you considered._

Add virtualbox allowed value for local.driver and integrate with VBoxManage using Multipass 1.11+ and VirtualBox 7.0.0+ to MacOS arm64 platforms

**Additional context**
_Add any other context or screenshots about the feature request here._

Asahi Linux is an incredible project, but the biggest risk of it is how it messes with APFS partitioning, possibly ruining your SSD in the process. Multipass is my preferred Linux-on-ASilicon right now, because of how safe it keeps my drives and how easy it is to manage, create, destroy, etc. However, Parallels is vastly better in its graphics performance, and is the only virtualization I have found to have reliable Wayland. QEMU consistently breaks with Wayland, even using UTM (MacOS QEMU GUI). I don't know how hard it is to integrate the Parallels driver to Multipass, but the VirtualBox driver is finally looking promising.

Start by locating the local.driver option handling and the platform-specific backend entry points, then trace how the existing QEMU driver integrates with virtualization tools. Check the proposed VBoxManage integration against Multipass 1.11+ and VirtualBox 7.0.0+ on macOS arm64. Done means the AppleVZ backend is available through the requested driver option and works on the stated platforms.

Written by the indexing model from the issue text.