Support Proxy Protocol

@dhuseby is already working on this.

Since Aug 24, 2023.

# Feature
Include [Proxy Protocol](https://www.haproxy.com/blog/haproxy/proxy-protocol/) to support the use of Load Balancers and Reverse Proxies.

## Background
The current behaviour of a libp2p node (e.g. lotus) behind a load balancer is to reflect a server's private IP or loopback interface as the source IP address of upstream peer connections established through a Load Balancer or Reverse Proxy.

This is a well known TCP load balancing issue, with a conventional but complex workaround to use Transparent Proxies. This requires kernel and iptables configuration, which creates a high barrier to success running libp2p nodes in this use case.

For Proxy Protocol to be fully supported, the downstream endpoint (libp2p node) should support Proxy Protocol 1 and 2 to establish the client's IP address (upstream libp2p peer).

## Current Behaviour
Behind an AWS Elastic Load Balancer:
```
$ lotus net peers
12D3KooWxxxxxxxxxxxxxxxxxxxxxxxxx, [/ip4/10.0.10.233/tcp/50202]
```

Behind a Reverse Proxy e.g. NGINX, HAPROXY:
```
$ lotus net peers
12D3KooWxxxxxxxxxxxxxxxxxxxxxxxxx, [/ip4/127.0.0.1/tcp/50202]
```

## Desired Behaviour
```
$ lotus net peers
12D3KooWxxxxxxxxxxxxxxxxxxxxxxxxx, [/ip4//tcp/]
```

## Current Pitfalls without Proxy Protocol support

- negative peer scores resulting from duplicate peer IPs (private IP reflection or loopback)
- restricted auditing capabilities