gemm block quantization infrastructure for llm decoder style

[nihui]

No description provided.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.95620% with 66 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.12%. Comparing base (13b6d53) to head (be7bb5f).

Files with missing lines	Patch %	Lines
src/layer/multiheadattention.cpp	91.14%	27 Missing ⚠️
src/layer/gemm.cpp	84.33%	26 Missing ⚠️
src/layer/vulkan/multiheadattention_vulkan.cpp	36.36%	7 Missing ⚠️
src/layer/vulkan/gemm_vulkan.cpp	50.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6814      +/-   ##
==========================================
+ Coverage   94.70%   95.12%   +0.41%     
==========================================
  Files         947      947              
  Lines      415846   416292     +446     
==========================================
+ Hits       393844   395999    +2155     
+ Misses      22002    20293    -1709     

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