[WIP]Support simpleomp for MSVC

[Jiang-Weibo]

Modified files:
simpleomp.cpp
CMakeLists.txt on the top directory for enabling openmp option on MSVC

[tencent-adm]

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.98%. Comparing base (5df5413) to head (56ed4e7).
Report is 4 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #5671       +/-   ##
===========================================
- Coverage   94.75%   89.98%    -4.77%     
===========================================
  Files         787      264      -523     
  Lines      248658    77271   -171387     
===========================================
- Hits       235604    69536   -166068     
+ Misses      13054     7735     -5319     

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