Add socks4/4a support

[nekohasekai]

Make socks support more complete.

[codecov-commenter]

Codecov Report

Merging #1269 (07bc4e2) into master (c58a372) will decrease coverage by 0.15%.
The diff coverage is 6.89%.

@@            Coverage Diff             @@
##           master    #1269      +/-   ##
==========================================
- Coverage   44.72%   44.57%   -0.16%     
==========================================
  Files         485      479       -6     
  Lines       29465    29454      -11     
==========================================
- Hits        13179    13128      -51     
- Misses      14884    14923      +39     
- Partials     1402     1403       +1     

Impacted Files	Coverage Δ
proxy/socks/client.go	0.87% <0.00%> (-0.26%)	⬇️
proxy/socks/config.pb.go	22.82% <5.26%> (-2.48%)	⬇️
infra/conf/socks.go	69.23% <27.27%> (-11.26%)	⬇️
testing/servers/tcp/tcp.go	81.81% <0.00%> (-5.46%)	⬇️
transport/internet/kcp/dialer.go	80.39% <0.00%> (-3.93%)	⬇️
transport/internet/websocket/connection.go	16.51% <0.00%> (-3.67%)	⬇️
testing/scenarios/common.go	70.68% <0.00%> (-3.45%)	⬇️
transport/internet/kcp/connection.go	69.61% <0.00%> (-2.21%)	⬇️
transport/internet/kcp/receiving.go	98.65% <0.00%> (-1.35%)	⬇️
transport/internet/filelocker_windows.go
... and 8 more

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[Loyalsoldier]

Please run go generate format.go to format files.

[nekohasekai]

Please run go generate format.go to format files.

Ok.

[xiaokangwang]

Thanks for your contribution. This pull request is ready to be merged.