Multiple simultaneous WSL2 kernels

Since the announcement that WSL2 kernels are going to be distributed through Windows Update, a few scenarios come to mind where it would be nice to have two simultaneous WSL2 VMs, one with the old kernel and one with the new kernel.

The most obvious example is spinning down a docker swarm running on the old WSL kernel while spinning it up on the new kernel. This could allow for a 0-downtime update.

In general, services listening on the network could be brought up on the new WSL kernel, then the virtual network interfaces could be swapped (or something of that nature -- I don't know exactly how to best orchestrate such a switchover).

Aside from these scenarios, there is also the case where users want a custom kernel for some VMs, but the stable kernel for most situations. While I don't know what the future will hold, take for example WireGuard, which existed as a kernel patch. A stable Windows-provided kernel would still be ideal for other services, but a secondary WSL2 instance could allow a patched kernel for trying new features.

It's possible this feature starts looking like it should integrate with the Hyper-V management panels, in which case, it should! I think it would be okay for an "advanced" WSL2 scenario to require Windows 10 Pro and up.

The issue mentions WSL2 kernels, Docker Swarm, virtual network interfaces, and possible Hyper-V integration, but no files, tests, or entry points. Start by reviewing how WSL2 instances and kernels are currently managed; done would mean supporting simultaneous instances with different kernels and a workable service or network transition.