Enhancing the support for query of /etc/hosts and simplifying the code.

[NathanFreeman]

Enhancing the support for query of /etc/hosts and simplifying the code.

# the contents of /etc/hosts file are as follow
127.0.0.1
127.0.0.1 localhost                www.baidu.com
                 127.0.0.1                       bbb.com  #ccc.com
# 127.0.0.1                         ddd.com

so , the programs can handle complex configurations of /etc/hosts file just like linux os.

Thanks.

[codecov]

Codecov Report

Merging #4349 (5ecb59f) into master (067f594) will increase coverage by 0.13%.
The diff coverage is 97.14%.

@@            Coverage Diff             @@
##           master    #4349      +/-   ##
==========================================
+ Coverage   50.66%   50.80%   +0.13%     
==========================================
  Files          72       72              
  Lines       14516    14528      +12     
==========================================
+ Hits         7355     7381      +26     
+ Misses       7161     7147      -14     

Impacted Files	Coverage Δ
src/network/dns.cc	88.38% <97.14%> (+1.26%)	⬆️
src/os/async_thread.cc	66.66% <0.00%> (-2.20%)	⬇️
src/server/master.cc	54.04% <0.00%> (-0.06%)	⬇️
src/coroutine/socket.cc	38.78% <0.00%> (-0.05%)	⬇️
src/os/signal.cc	73.61% <0.00%> (ø)
src/protocol/base.cc	63.15% <0.00%> (ø)
src/protocol/http.cc	30.09% <0.00%> (ø)
src/protocol/mqtt.cc	0.00% <0.00%> (ø)
src/protocol/redis.cc	58.51% <0.00%> (ø)
src/os/process_pool.cc	57.89% <0.00%> (ø)
... and 6 more

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[matyhtf]

@NathanFreeman 请添加微信 19921030512 详细沟通

[zmyWL]

代码没问题