Add Networking metadata to Libvirt XML

### The required feature described as a wish

Libvirt allows for adding Metadata to the XML of a Domain: https://libvirt.org/formatdomain.html#general-metadata

We can use this Metadata to add additional information of the Instance so that it can be used by Libvirt hooks: https://libvirt.org/hooks.html#etc-libvirt-hooks-qemu

My proposal is to add basic IP address information to the XML:

```

```

Hooks can prepare additional firewalling or routing on the host while it is booted, this is up to the admin to decide.

首先跟踪 CloudStack 如何生成 Libvirt 域 XML，并查看 issue 中链接的 Libvirt 域元数据和 hook 文档。当生成的 XML 为适用的 IPv4 和 IPv6 网络包含所请求的网络地址元数据（包括地址、前缀、族、桥接和 VLAN 值）时，工作即完成。

由索引模型根据 Issue 内容生成。