Use the built-in Ranch PROXY protocol support

[essen]

This set of PRs is ready. Full set listed in rabbitmq/rabbitmq-common#279

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[essen]

Depends on rabbitmq/rabbitmq-common#282 + a few tiny changes.

[acogoluegnes]

Steps to test: https://github.com/acogoluegnes/rabbitmq-proxy-protocol

[michaelklishin]

This and related PRs have been backported to v3.7.x.