Support Adguard Android itself to access the network through a proxy

### Issue Details

我是一名中国用户，使用 adguard 的 vpn 模式代理其他应用，再由 socks 代理 adguard 出站流量，其他应用都能正常访问。但是当我在 Adguard 内导入 https://raw.githubusercontent.com/ 上的规则时却失败了，因为我的网络在不代理的情况下无法访问这个网站，因此希望 Adguard 本身的流量也支持走下级代理。

---- translate:

I'm a Chinese user who uses AdGuard's VPN mode to proxy other apps, and then Socks proxies AdGuard outbound traffic, and other apps can be accessed normally. But when I imported the rules on the https://raw.githubusercontent.com/xxx within Adguard, it failed, because my network can't access the site without a proxy, so I want Adguard's own traffic to support a subordinate proxy as well

### Proposed solution

希望与 windows 版本一样，让 adguard android 本身也支持通过代理访问网络：
---- translate
Hopefully, as with the Windows version, AdGuard Android natively supports network access via a proxy：


Chinese language screenshot


### Alternative solution

_No response_