feat(instances): a VM's disks as cards, its CD-ROM drives above them

Settings > Disk was a bold title with an unlabelled "+", a CD-ROM row
in an input group, and a table whose actions were four alike icons.
The owner chose this layout from three rendered options:

- Removable media: each CD-ROM drive a card with its device, bus and
  image, the ISO select and Mount (or Unmount), and Detach; "Add
  CD-ROM" by the heading.
- Disks: a card each; one disk spans the row, two or more sit side by
  side from md, and the device details are capped at 32rem so values
  stay near their labels. The capacity large,
  the used size, the pool and the source path, the device's settings
  under "Device details" (they were in a popover), and labelled Edit,
  Move, Detach and Delete (danger) in its footer; "Add disk" by the
  heading.
- While the VM runs, "Add CD-ROM" adds the drive on the SCSI bus, and
  a SCSI drive can be detached: IDE and SATA drives cannot be plugged
  into or out of a running VM, SCSI ones can. Adding a drive was
  disabled while the VM ran. One line says so, and why detaching other
  drives and detaching or deleting disks waits for a shutdown, instead
  of each button alone being greyed.

The forms, their fields and actions are unchanged. The edit dialog of each
disk is titled with its device, and its fields' ids carry the disk's
number: the dialogs of two disks had the same ids, and the title was not
the dialog's label.

static/icon_cache/disc_None_None_None.svg

@@ -0,0 +1,11 @@
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+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-disc" viewBox="0 0 16 16">
+	
+  
+	<path d="M8 15A7 7 0 1 1 8 1a7 7 0 0 1 0 14m0 1A8 8 0 1 0 8 0a8 8 0 0 0 0 16"/>
+	
+  
+	<path d="M10 8a2 2 0 1 1-4 0 2 2 0 0 1 4 0M8 4a4 4 0 0 0-4 4 .5.5 0 0 1-1 0 5 5 0 0 1 5-5 .5.5 0 0 1 0 1m4.5 3.5a.5.5 0 0 1 .5.5 5 5 0 0 1-5 5 .5.5 0 0 1 0-1 4 4 0 0 0 4-4 .5.5 0 0 1 .5-.5"/>
+	
+
+</svg>