[WIP] Forward compatibility with upcoming Promise v3

[clue]

Builds on top of https://github.com/reactphp/promise/pull/75, https://github.com/reactphp/promise/pull/213, https://github.com/reactphp/promise/pull/138, https://github.com/reactphp/socket/pull/214 and https://github.com/reactphp/promise-stream/pull/20 Also builds on top of dev updates in https://github.com/clue/reactphp-block/pull/61, https://github.com/clue/reactphp-http-proxy/pull/44, https://github.com/clue/reactphp-socks/pull/106 and https://github.com/clue/reactphp-ssh-proxy/pull/35