Feature arm fp16 op

[powerpwang]

1. Support ARMv8.2 FP16
2. FP16 OP: Add, BatchNorm, Concat, Conv, Deconv, Pool, Permute, PReLU, ReLU, ReLU6, Sigmoid, Softmax

[codecov-io]

Codecov Report

Merging #588 (1d6e3b2) into master (5661ef9) will increase coverage by 2.33%.
The diff coverage is 24.19%.

@@            Coverage Diff             @@
##           master     #588      +/-   ##
==========================================
+ Coverage   30.95%   33.28%   +2.33%     
==========================================
  Files         290      287       -3     
  Lines        9298     8331     -967     
==========================================
- Hits         2878     2773     -105     
+ Misses       6420     5558     -862     

Impacted Files	Coverage Δ
include/tnn/core/common.h	100.00% <ø> (ø)
source/tnn/interpreter/layer_param.h	0.00% <ø> (ø)
...nn/optimizer/net_optimizer_insert_fp16_reformat.cc	14.45% <0.00%> (-1.13%)	⬇️
...tnn/optimizer/net_optimizer_insert_fp16_reformat.h	100.00% <ø> (ø)
source/tnn/utils/blob_converter_default.cc	86.47% <0.00%> (-1.60%)	⬇️
source/tnn/utils/blob_dump_utils.cc	0.61% <0.00%> (+0.61%)	⬆️
source/tnn/utils/cpu_utils.cc	13.33% <ø> (-2.46%)	⬇️
source/tnn/utils/random_data_utils.cc	64.70% <ø> (+2.20%)	⬆️
source/tnn/utils/naive_compute.cc	59.60% <71.42%> (+3.59%)	⬆️
source/tnn/utils/data_type_utils.cc	30.00% <0.00%> (-10.00%)	⬇️
... and 178 more

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[seanxcwang]

merge完master之后，half的测试没了