Add support for Websocket endpoints

[fortuna]

This tracks the work towards supporting Websocket in the Outline client. For the server-side work, see Jigsaw-Code/outline-ss-server#228.

Done

As you can see, we had to re-write major portions of the code. Most of the PRs below are large or extra-large.

Implement Websocket logic

• feat(client): add Websocket support to the Outline Client config #2351
• feat(x): use endpoint instead of dialer for websocket outline-sdk#368
• fix(x): fix Websocket code outline-sdk#367
• chore(x): implement WS client with Gorilla outline-sdk#361
• feat: create WebSocket Reverse Proxy outline-sdk#202
• feat(x): add Websocket client support outline-sdk#231

Implementing new config parsing in Go

• feat(client): introduce extensible YAML config #2329
• refactor(client): make parsing async and config an opaque string #2324

Make it practical to add new native methods without changing every platform

• chore(client): clean up errors #2346
• chore(client): clean up invokeMethod error propagation #2336
• refactor(client): create Typescript MethodChannel on all platforms #2298

Remove explicit dependencies on Shadowsocks from Typescript code

• refactor(client): reduce config library surface #2269
• refactor(client): more config cleanup and consolidation #2265
• refactor(client): clean up transport in Typescript #2192
• refactor(client): replace references to Shadowsocks #2182
• refactor(client): revamp Tunnel code #2072

Remove explicit dependencies on Shadowsocks across the stack

• refactor(client): preliminary wiring of service name #2075
• refactor(client): decouple Typescript VPN API from individual servers #2105

Remove explicit dependencies on Shadowsocks from Electron code

• chore(client): pass transport as string in electron, to the extent possible #2142

Remove explicit dependencies on Shadowsocks from Android and Apple code

• chore(client): pass transport as string on Android and Apple #2141
• Apple
  • feat(client): support IPv6 on Apple, pass transport config around as string in Apple code #2132
  • fix(client): properly wait for start to be done #2117
  • refactor(client): delete OutlineLauncher and OutlineTunnelStore #2114
  • refactor(client): clean up Apple VPN code #2113
  • refactor(client): clean up App Groups #2090
  • refactor(client/cordova/apple): assorted cleanups #2071
  • build(client/cordova/apple/ios): upgrade to iOS 13.1 #2057

Make it possible to change and build the Go code together with the app

• chore(cordova/android): use src/tun2socks, not precompiled third_party version #1816
• chore: add outline-go-tun2socks, except android #1744