RVV: Shuffle Channel

[thelastlin]

RVV: Shuffle Channel, fp32/fp16/bf16, with elempack support

[codecov-commenter]

Codecov Report

Merging #4907 (8fd5473) into master (c45c01c) will increase coverage by 4.47%.
Report is 77 commits behind head on master.
The diff coverage is 92.00%.

@@             Coverage Diff             @@
##           master    #4907       +/-   ##
===========================================
+ Coverage   89.81%   94.28%    +4.47%     
===========================================
  Files         306      717      +411     
  Lines       86875   219734   +132859     
===========================================
+ Hits        78024   207183   +129159     
- Misses       8851    12551     +3700     

Files	Coverage Δ
src/layer/riscv/shufflechannel_riscv.cpp	92.00% <92.00%> (ø)

... and 601 files with indirect coverage changes

[nihui]

其实 shufflechannel 优化挺难的，加油

[thelastlin]

newlib-rv64gc-gcc failed due to the compiler not supporting some RISC-V Vector intrinsics like vlm_v_b8 or vset_v_f32m1_f32m4.

But it seems that the compiler shouldn't enable RVV intrinsics support at this CI, or we might need upgrade the compiler used by this CI?