[WIP] vulkan int8 packing quantize dequantize requantize

[nihui]

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.41118% with 28 lines in your changes missing coverage. Please review.

Project coverage is 95.81%. Comparing base (7557f5c) to head (2110e77). Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
src/gpu.cpp	83.78%	12 Missing :warning:
src/allocator.cpp	9.09%	10 Missing :warning:
src/layer/vulkan/dequantize_vulkan.cpp	98.44%	2 Missing :warning:
src/layer/vulkan/quantize_vulkan.cpp	98.36%	2 Missing :warning:
src/layer/vulkan/requantize_vulkan.cpp	98.54%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3731      +/-   ##
==========================================
- Coverage   95.81%   95.81%   -0.01%     
==========================================
  Files         831      834       +3     
  Lines      264948   265433     +485     
==========================================
+ Hits       253851   254315     +464     
- Misses      11097    11118      +21     

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[github-actions[bot]]

The binary size change of libncnn.so (bytes)

architecture	base size	pr size	difference
x86_64	15593968	15661624	+67656 :warning:
armhf	6602932	6657988	+55056 :warning:
aarch64	9983872	9989392	+5520 :warning: