Fix: resize GuestOS disk

[songponssw]

Try to fix: #1448

How Lima edit disk

• The limactl edit updates the disk value to the store. It does not resize disk image. Users have to manually resize by qemu-img
• Does not support --shrink (fails to start instance)

What I did

• create a limactl disk add command to add an existing qcow2 disk to Lima.
• To update GuestOS disk, before start instance, It adds a diffdisk of the instance to Lima, resize, and delete.

[songponssw]

This implementation works fine for increasing the disk size.
However, it returns an error when shrinking, as disk shrinking is not supported.

[AkihiroSuda]

Needs rebase

[songponssw]

Summary of Latest Review:

1. DiskDir is dedicated to additional disks.
   • I've updated the implementation by creating a new ResizeDiffDisk function, which directly resizes the diffdisk.
2. Calling inst.inspect() twice:
   • The editAction function returns instance.Start which doesn’t update the validated configuration in the store or the instance yet.
   • The second call to inst.inspect() is to apply the new configuration.
   • The first call to inst.inspect() checks whether the instance exists and is running.

[jandubois]

Note that #3513 moved the qemu-img functions to pkg/qemu/imgutil.

[songponssw]

I pushed the same code as before cleaning up the commits, but the test workflow is still failing.

[AkihiroSuda]

Thanks

[songponssw]

Thanks a lot for reviewing!