Allow selection of storage pool when creating a new VM

[JeffWDH]

While creating a new VM you currently have an option to create a new volume, use no storage, or pick a pre created disk image from a storage pool. When selecting the new volume option the destination is hard coded to the "default" storage pool. It would be great to have the ability to select from the list of available storage pools.

[niklas88]

Ran into this as well. Turns out once upon a time this was already reported and fixed. Seems someone pushed for simplicity a bit too hard and removed this feature again.
cockpit-project/cockpit#11479