[grenoble] Add pneyron-spack-vm persistent VM

Add a persistant virtual machine for experimenting with spack.

data/grid5000/sites/lille/servers/pneyron-spack-vm.json

+{
+  "expire": "2024-03",
+  "kind": "virtual",
+  "network_adapters": {
+    "default": {
+      "ip": "172.16.29.1"
+    }
+  },
+  "type": "server",
+  "uid": "pneyron-spack-vm"
+}
\ No newline at end of file