QEMU virtio-mem support

[Liassica]

The virtio-mem page says that QEMU has supported virtio-mem since QEMU version v5.1.0-rc1; the current version of QEMU in nixpkgs-25.05 is 9.2.4, but this tool still throws an error when trying to use hotplugMem/hotpluggedMem with QEMU.

[SuperSandro2000]

A PR would be welcome to update the qemu code to support this.