feat: Support proxy config and env vars for HTTP, TCP and TLS Probers

[haoel]

close #193

Code changes:

• Add the proxy configuration to support socks5 proxy for TLS and TCP probes.
• Support the $ALL_PROXY environment variable for TLS and TCP probes.
• Support the $HTTP_PROXY and $HTTPS_PROXY environment variable for HTTP probe

[codecov-commenter]

Codecov Report

Merging #194 (5973289) into main (46f758f) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #194      +/-   ##
==========================================
+ Coverage   94.40%   94.44%   +0.03%     
==========================================
  Files          49       49              
  Lines        4025     4051      +26     
==========================================
+ Hits         3800     3826      +26     
  Misses        157      157              
  Partials       68       68              

Impacted Files	Coverage Δ
eval/extract.go	100.00% <ø> (ø)
probe/http/http.go	96.53% <ø> (ø)
probe/base/base.go	100.00% <100.00%> (ø)
probe/tcp/tcp.go	100.00% <100.00%> (ø)
probe/tls/tls.go	100.00% <100.00%> (ø)

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[proditis]

I couldnt get the socks5 to work with environment variables, but i am not sure i tested right. every format combination i tried with ALL_PROXY had no effect.
HTTP_PROXY and HTTPS_PROXY work as expected each affects only their corresponding protocol.

[haoel]

I couldnt get the socks5 to work with environment variables, but i am not sure i tested right. every format combination i tried with ALL_PROXY had no effect. HTTP_PROXY and HTTPS_PROXY work as expected each affects only their corresponding protocol.

By using the following command, you can create a SOCKS5 proxy. then you can set ALL_PROXY=socks5://127.0.0.1:1080

ssh -D 1080 -qCN [email protected]

Besides, you can set a wrong socks5 server, such as ALL_PROXY=socks5://127.0.0.1:1024, and you can see the error message dial tcp 127.0.0.1:1024: connect: connection refused for TCP or TLS probe.