Support for proxy protocol v2

[UltraInstinct14]

Is your feature request related to a problem? Please describe.
In many NAT nodes used by loxilb, the original sourceIP gets obfuscated at the endpoint. It might result in problem of accounting various things related to the original source such as abuse, DDOS attacks or to keep simple statistical counts.

Describe the solution you'd like
loxilb needs to implement proxy protocol v2. Currently many web-servers already support it

Describe alternatives you've considered
N/A

Additional context
https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt