outbound proxy protocol miss in various scenarios

[m-matth]

With proxy.config.http.proxy_protocol_out=2 enabled, we identified some cases when the proxy protocol packet is not send to the origin.

• when session is private on clear http origin connection , i created a small PR for quick fix purposes only (ProxyProtocol: add missing proxy protocol on clear http/1.1 private session #12336)

• when client use http/2 and origin is http/1.1, and multiple h2 streams are dispatched to origin

• when origin use tls

Tested on ATS 10.0.6