feat: add http 1.1 trailer

[huanghantao]

#3417

[codecov]

Codecov Report

Merging #3485 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3485      +/-   ##
==========================================
+ Coverage   42.14%   42.19%   +0.05%     
==========================================
  Files          75       75              
  Lines       14386    14482      +96     
==========================================
+ Hits         6063     6111      +48     
- Misses       8323     8371      +48     

Impacted Files	Coverage Δ
src/server/process.cc	59.82% <0.00%> (-0.52%)	⬇️
src/reactor/base.cc	60.22% <0.00%> (-0.35%)	⬇️
src/server/port.cc	45.33% <0.00%> (-0.33%)	⬇️
src/network/client.cc	44.34% <0.00%> (-0.29%)	⬇️
src/core/base.cc	36.60% <0.00%> (-0.26%)	⬇️
src/coroutine/system.cc	35.03% <0.00%> (-0.16%)	⬇️
src/server/master.cc	50.63% <0.00%> (-0.12%)	⬇️
src/os/process_pool.cc	19.40% <0.00%> (-0.05%)	⬇️
src/coroutine/file_lock.cc	2.85% <0.00%> (-0.05%)	⬇️
src/core/log.cc	52.69% <0.00%> (+0.28%)	⬆️
... and 4 more

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