feat(vm-provision): declare the guest agent per guest OS, Linux only

Follows napalm-device-types 3.0, which replaces GUEST_AGENT_PACKAGES /
GUEST_AGENT_RUNCMD with GUEST_AGENTS = {guest_os: (packages, runcmd)}.
VMware lists Linux with open-vm-tools, as before, and refuses any other
guest_os before anything is created: BSD guests on VMware are optional
for now (NetOrk/netork#801).

The NoCloud network-config moved to napalm-device-types
(`provisioning.network_config`), which Proxmox now uses as well; the seed
module's copy is gone, and the tests check that the generic one is used.

tests/test_provisioning.py

@@ -152,6 +152,18 @@ class TestCreate:
         staged.cache.return_value.vmdk.assert_not_called()
         staged.import_ovf.assert_not_called()
 
+    @pytest.mark.parametrize("guest_os", ["freebsd", "openbsd"])
+    def test_a_guest_other_than_linux_is_refused_before_anything_happens(
+        self, driver, staged, guest_os
+    ):
+        with pytest.raises(ValueError, match=guest_os):
+            _create(driver, guest_os=guest_os)
+        staged.cache.return_value.vmdk.assert_not_called()
+        staged.import_ovf.assert_not_called()
+
+    def test_linux_is_the_default_guest(self, driver, staged):
+        assert _create(driver, guest_os="linux")["vmid"] == "uuid-99"
+
     def test_placement_refusal_is_a_runtime_error(self, driver, staged):
         with patch.object(prov, "choose_placement", side_effect=ValueError("no host")):
             with pytest.raises(RuntimeError, match="no host"):