Support for PROXYv2 in gitlab-pages
This patch implements support for the PROXYv2 protocol, which recently landed in gitlab-pages (gitlab-org/gitlab-pages!278 (merged)). This will allow us to propagate remote_ip
from the client through one or more layers of TCP load balancing.
In the future it will also allow us to send pages traffic through cloudflare.
cc @vshushlin
refs https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/11902