[Feature Request]: support FS DISCARD for virtio-blk

[ihexon]

I observed that the virtio-blk device in libkrun does not support the discard command, which results in the following error when I run:

fstrim -v /mnt/vda/
fstrim: /mnt/vda/: the discard operation is not supported

In Orbstack there is no issue when I do fstrim.

I used krun_add_disk to add a sparse file (which created by truncate -s 10G ~/data1.img) as /dev/vda to the guest.

and I found that krun_add_disk does not expose discard related control parameters. In qemu, I can pass the discard=unmap like this:

<disk>
  <driver  name='qemu' type='qcow2' discard='unmap' detect_zeroes='unmap'>
  <target dev='...' bus='scsi'>
</disk>

Does libkrun's virtio-blk implementation support the DISCARD instruction?