Add DeformableConv2D

[miemie2013]

Add DeformableConv2D

[tencent-adm]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

Merging #4070 (c405dfd) into master (4f414c1) will decrease coverage by 0.21%.
The diff coverage is 97.60%.

@@            Coverage Diff             @@
##           master    #4070      +/-   ##
==========================================
- Coverage   94.41%   94.20%   -0.22%     
==========================================
  Files         745      744       -1     
  Lines      178496   178509      +13     
==========================================
- Hits       168533   168162     -371     
- Misses       9963    10347     +384     

Impacted Files	Coverage Δ
src/layer/deformableconv2d.cpp	97.19% <97.19%> (ø)
src/layer/x86/deformableconv2d_x86.cpp	97.91% <97.91%> (ø)
src/command.cpp	72.70% <0.00%> (-14.94%)	⬇️
src/layer/riscv/convolution_3x3_pack1ton_fp16s.h	89.14% <0.00%> (-10.86%)	⬇️
src/pipeline.cpp	58.69% <0.00%> (-2.18%)	⬇️
src/layer/vulkan/reshape_vulkan.cpp	92.01% <0.00%> (-2.14%)	⬇️
src/layer/vulkan/packing_vulkan.cpp	81.70% <0.00%> (-1.88%)	⬇️
src/layer/vulkan/permute_vulkan.cpp	96.99% <0.00%> (-1.60%)	⬇️
src/layer/vulkan/reorg_vulkan.cpp	96.35% <0.00%> (-1.57%)	⬇️
src/layer/vulkan/pixelshuffle_vulkan.cpp	96.35% <0.00%> (-1.57%)	⬇️
... and 53 more

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[nihui]

hi, please enable github action in your fork to make code-format bot work properly

[nihui]

please add unittest for new operator
please add new operator doc in docs/developer-guide/operators.md

[nihui]

Thanks for your contribution !