in-house vulkan loader

[nihui]

• resolve link issue
• test windows
• doc
• VK_ICD_FILENAMES
• default to static moltenvk on apple platforms

ncnn::create_gpu_instance();
ncnn::create_gpu_instance("libvulkan.so");
ncnn::create_gpu_instance("libvulkan.so.1");
ncnn::create_gpu_instance("vulkan-1.dll");
ncnn::create_gpu_instance("libvulkan.dylib");
ncnn::create_gpu_instance("libvulkan.1.dylib");
ncnn::create_gpu_instance("libMoltenVK.dylib");
ncnn::create_gpu_instance("/usr/lib/libvulkan_radeon.so");
ncnn::create_gpu_instance("/usr/lib64/libvulkan_radeon.so");
ncnn::create_gpu_instance("/usr/lib64/libvulkan_intel.so");
ncnn::create_gpu_instance("/usr/lib64/libvulkan_lvp.so");
ncnn::create_gpu_instance("/vendor/lib64/hw/vulkan.adreno.so");
ncnn::create_gpu_instance("/vendor/lib64/hw/vulkan.rk30board.so");
ncnn::create_gpu_instance("/vendor/lib64/hw/vulkan.rk3399.so");
ncnn::create_gpu_instance("/data/local/tmp/vulkan.ad07XX.so");

[codecov-commenter]

Codecov Report

Merging #5130 (c781870) into master (31e3159) will decrease coverage by 5.02%.
Report is 1 commits behind head on master.
The diff coverage is n/a.

❗ Current head c781870 differs from pull request most recent head 5dc0c99. Consider uploading reports for the commit 5dc0c99 to get more accurate results

@@             Coverage Diff             @@
##           master    #5130       +/-   ##
===========================================
- Coverage   94.70%   89.69%    -5.02%     
===========================================
  Files         776      261      -515     
  Lines      241462    73762   -167700     
===========================================
- Hits       228674    66159   -162515     
+ Misses      12788     7603     -5185     

Files	Coverage Δ
src/allocator.h	87.50% <ø> (ø)
src/mat.h	91.25% <ø> (-1.53%)	⬇️

... and 754 files with indirect coverage changes