ability to import standalone qemu instances to lima to manage

### Description

lima can create VMs based on QEMU. I could also create VMs based on QEMU, in those cases, I'd like to import this VM to lima to be managed by it like the env driver of buildx which lets you create a buildkitd daemon separetely and add it as a builder instance to buildx.

cc: @AkihiroSuda @dentrax