Adds an extra_volumes property to the tofu compute mapping to allow defining volumes which OpenTofu will create and attach to compute nodes. Useful for simulating additional disks present in baremetal instances using virtualized instances.

Note that:

• Unlike the default home and state volumes attached to the control node, compute volumes defined this way are not automatically formatted or mounted.
• Volumes are attached after instance creation and the path under /dev/{v,s}d* may not reflect the ordering in the extra_volumes property and may change across reboots. Use e.g. /dev/disk/by-path/ for mounts etc.
• As long as volume-backed compute instances are not used, OpenTofu will update instances in place (i.e. reimage) to change the node image, even with extra_volumes specified.