c_api: expose Mat border processing api

[Mek101]

Adds ncnn_copy_make_border, ncnn_copy_make_border_3d, ncnn_copy_cut_border and ncnn_copy_cut_border_3d to the C api

[tencent-adm]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

Merging #4855 (c1e4318) into master (e8645e9) will increase coverage by 0.36%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #4855      +/-   ##
==========================================
+ Coverage   94.53%   94.89%   +0.36%     
==========================================
  Files         779      779              
  Lines      221835   223186    +1351     
==========================================
+ Hits       209706   211795    +2089     
+ Misses      12129    11391     -738     

Impacted Files	Coverage Δ
src/c_api.cpp	40.58% <0.00%> (-0.98%)	⬇️

... and 41 files with indirect coverage changes

[Mek101]

Can anyone approve the CI run please?

[nihui]

enable github action in your forked repo to let code-format work properly

[Mek101]

Set as r/w

[Mek101]

Can anyone approve the CI run please?

[Mek101]

Found the issue

[nihui]

Thanks for your contribution !