I deliberately kept this as an unregistertimeout because that was the
intent. In the future we could change this to a UDPConnConfig if we want
to pass multiple values here.
The idea of this PR is simply to add a configurable unregister UDP
timeout.
- Vendored the capnproto library to cloudflared.
- Added capnproto schema defining application protocol.
- Added Pogs and application level read write of the protocol.