[Feature] support ada module and training

[plyfager]

1. Support ada augment.
2. Support ADAStyleGAN2Discriminator and its training.

[codecov]

Codecov Report

Merging #276 (68ab951) into master (0c5643e) will decrease coverage by 0.13%.
The diff coverage is 69.15%.

@@            Coverage Diff             @@
##           master     #276      +/-   ##
==========================================
- Coverage   74.85%   74.71%   -0.14%     
==========================================
  Files         141      145       +4     
  Lines       10484    10909     +425     
  Branches     2064     2144      +80     
==========================================
+ Hits         7848     8151     +303     
- Misses       2151     2220      +69     
- Partials      485      538      +53     

Flag	Coverage Δ
unittests	74.71% <69.15%> (-0.14%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmgen/core/evaluation/metrics.py	75.52% <ø> (ø)
.../architectures/stylegan/ada/grid_sample_gradfix.py	61.90% <61.90%> (ø)
mmgen/models/architectures/stylegan/ada/augment.py	63.56% <63.56%> (ø)
...gen/models/architectures/stylegan/ada/upfirdn2d.py	73.33% <73.33%> (ø)
mmgen/models/architectures/stylegan/ada/misc.py	81.81% <81.81%> (ø)
...chitectures/stylegan/generator_discriminator_v2.py	88.83% <94.44%> (+1.05%)	⬆️
...chitectures/stylegan/modules/styleganv3_modules.py	98.37% <100.00%> (+3.63%)	⬆️
mmgen/models/gans/static_unconditional_gan.py	71.66% <100.00%> (+2.10%)	⬆️
mmgen/models/architectures/stylegan/mspie.py	91.58% <0.00%> (ø)
... and 1 more

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