## Summary
To prevent bad eyeballs and severs to be able to exhaust the quic
control flows we are adding the possibility of having a timeout
for a write operation to be acknowledged. This will prevent hanging
connections from exhausting the quic control flows, creating a DDoS.
Creates an abstraction over UDP Conn for origin "connection" which can
be useful for future support of complex protocols that may require
changing ports during protocol negotiation (eg. SIP, TFTP)
In addition, it removes a dependency from ingress on connection package.
Reuses HTTPProxy's Roundtrip method to directly proxy websockets from
eyeball clients (determined by websocket type and ingress not being
connection oriented , i.e. Not ssh or smb for example) to proxy
websocket traffic.
All header transformation code from h2mux has been consolidated in the connection package since it's used by both h2mux and http2 logic.
Exported headers used by proxying between edge and cloudflared so then can be shared by tunnel service on the edge.
Moved access-related headers to corresponding packages that have the code that sets/uses these headers.
Removed tunnel hostname tracking from h2mux since it wasn't used by anything. We will continue to set the tunnel hostname header from the edge for backward compatibilty, but it's no longer used by cloudflared.
Move bastion-related logic into carrier package, untangled dependencies between carrier, origin, and websocket packages.