Add Riverrun TCP Stream Modifier into V2Ray

[xiaokangwang]

Riverrun is a TCP Stream Modifier that try to reduce the entropy of traffics in order to bypass some kind of traffic classification, including the block of fully encrypted traffic. This version includes the simplest integration that use a seed to automatically derivate all parameters and apply the transformation to the entire stream.

The deterministic random number generator code is written by an author that is not personally known to us, with 2-BSD license. I think it is fine to include it, but in the worst case this part can be rewritten with a incompatible protocol change. Other codes are awaiting relicense confirmation from their authors.

To run one of its client:
v2ray run -format jsonv5 -c client.json

{
  "log": {
    "error": {
      "level": "Debug",
      "type": "Console"
    },
    "access": {
      "type": "None"
    }
  },
  "outbounds": [
    {
      "protocol": "vmess",
      "settings": {
        "port": 44122,
        "uuid": "480b5e93-a450-47d0-8a9a-cdac889488e5",
        "address": "127.0.0.1"
      },
      "streamSettings": {
        "transport": "tcp",
        "transportSettings": {
          "headerSettings": {
            "@type": "types.v2fly.org/v2ray.core.transport.internet.headers.riverrun.Config",
            "seed": "riverrun_64hw2d6o7tlupu9jufl3hr68kbwguewcg2rs"
          }
        }
      }
    }
  ],
  "inbounds": [
    {
      "protocol": "socks",
      "settings": {
        "udpEnabled": true,
        "address": "127.0.0.1",
        "packetEncoding": "Packet"
      },
      "port": 10808
    }
  ]
}

To run one of its client:
v2ray run -format jsonv5 -c client.json

{
  "log": {
    "error": {
      "level": "Debug",
      "type": "Console"
    },
    "access": {
      "type": "None"
    }
  },
  "outbounds": [
    {
      "protocol": "freedom"
    }
  ],
  "inbounds": [
    {
      "protocol": "vmess",
      "settings": {
        "users": [
          "480b5e93-a450-47d0-8a9a-cdac889488e5"
        ]
      },
      "port": 44122,
      "streamSettings": {
        "transport": "tcp",
        "transportSettings": {
          "headerSettings": {
            "@type": "types.v2fly.org/v2ray.core.transport.internet.headers.riverrun.Config",
            "seed": "riverrun_64hw2d6o7tlupu9jufl3hr68kbwguewcg2rs"
          }
        }
      }
    }
  ]
}

Note to self: squash on merge.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 19.62617% with 86 lines in your changes are missing coverage. Please review.

Project coverage is 35.56%. Comparing base (49b5068) to head (2028e56).
Report is 1 commits behind head on master.

Files	Patch %	Lines
transport/internet/headers/riverrun/riverrun.go	2.27%	42 Missing and 1 partial ⚠️
transport/internet/headers/riverrun/config.pb.go	32.78%	39 Missing and 2 partials ⚠️
...port/internet/headers/riverrun/errors.generated.go	0.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2946      +/-   ##
==========================================
- Coverage   35.60%   35.56%   -0.05%     
==========================================
  Files         729      732       +3     
  Lines       41612    41719     +107     
==========================================
+ Hits        14818    14838      +20     
- Misses      25161    25246      +85     
- Partials     1633     1635       +2     

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