adding multiplex support to WATER

[WendelHime]

This is a draft PR for testing multiplex support for WATER. With this implementation as is, the proxy is able to receive connections but unable to respond/proxy the information and receives an error.

DEBUG cmux: listener.go:88 Error creating multiplexed session, probably just means that the underlying connection was closed: invalid protocol
[WATM reverse v1] read error: errno 6
2024/11/11 19:07:54 worker: unfairWorker: sourceConn.Read: errno 6
[WATM reverse v1] read error: errno 6

Update: The error above was only happening because the client (flashlight) wasn't using the multiplex implementation. After enabling at getlantern/flashlight#1439, the connection worked with a few interruptions