[WIP] Update handler vhost-nvme for QEMU

[vk-en]

A patch for QEMU that adds functionality to create the vhost-kernel-nvme handler. This change adds a new --device "vhost-kernel-nvme" to qemu. For this functionality to work, you need the second part (vhost-nvme) of the kernel-side patch, which creates the required character device /dev/vhost-nvme.

[rouming]

out of the curiosity: what is the difference to the spdk approach: https://gerrithub.io/c/spdk/qemu/+/409094/1 ? or to the vhost-nvme in qemu: https://qemu-devel.nongnu.narkive.com/qwJ8pbxp/rfc-patch-0-9-vhost-nvme-new-qemu-nvme-backend-using-nvme-target#post1 ??

[vk-en]

@rouming Of course, we worked with these patches. And we took them as a basis. Also, as far as I know, there are older versions of this implementation. These patches are not very stable, and require significant improvements, in our case, for sure.