layernorm+add support int8

[tpoisonooo]

• 实现了 int8 layernorm，imagenet1k 只量化 LN 精度 84.01->83.68

[codecov-commenter]

Codecov Report

Merging #4115 (9bd2ac4) into master (b4ba207) will decrease coverage by 1.79%. The diff coverage is 97.28%.

@@             Coverage Diff             @@
##           master    #4115       +/-   ##
===========================================
- Coverage   94.42%   92.63%    -1.80%     
===========================================
  Files         747      204      -543     
  Lines      178769    35282   -143487     
===========================================
- Hits       168811    32684   -136127     
+ Misses       9958     2598     -7360     

Impacted Files	Coverage Δ
src/layer/convolution.cpp	98.05% <ø> (+3.59%)	:arrow_up:
src/layer/layernorm.cpp	43.37% <90.32%> (-54.85%)	:arrow_down:
src/layer/mathfun.h	100.00% <100.00%> (ø)
src/layer/multiheadattention.cpp	100.00% <100.00%> (+6.76%)	:arrow_up:
src/layer/riscv/convolution_3x3_pack1ton_fp16s.h	89.14% <0.00%> (-10.86%)	:arrow_down:
src/cpu.cpp	52.09% <0.00%> (-10.03%)	:arrow_down:
src/allocator.cpp	73.98% <0.00%> (-3.07%)	:arrow_down:
src/layer/memorydata.cpp	70.37% <0.00%> (-2.05%)	:arrow_down:
src/allocator.h	85.71% <0.00%> (-1.79%)	:arrow_down:
... and 683 more

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[lgtm-com[bot]]

This pull request introduces 1 alert when merging 9bd2ac455f278595ba42217292bc2695144a6c6b into 00c08d7bda53b10dd488af3aa65de9c6dbe30cfb - view on LGTM.com

new alerts:

• 1 for FIXME comment

[lgtm-com[bot]]

This pull request introduces 1 alert when merging ac0d745848f95993287cf4346515253414035ea5 into 0b3d157a627563e05401de4bcb5f94177e8a7ddc - view on LGTM.com

new alerts:

• 1 for FIXME comment

[lgtm-com[bot]]

This pull request introduces 1 alert when merging fa009764c573bd60b324bf834239c4381415994b into 0b3d157a627563e05401de4bcb5f94177e8a7ddc - view on LGTM.com

new alerts:

• 1 for FIXME comment

[lgtm-com[bot]]

This pull request introduces 2 alerts when merging 17218cc894e28bfae813e2a16fce4ac714f5044b into 0b3d157a627563e05401de4bcb5f94177e8a7ddc - view on LGTM.com

new alerts:

• 1 for Function declared in block
• 1 for FIXME comment