Add arcface head

[zzc98]

Motivation

Support ArcFace loss.

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects, like MMDet or MMSeg.
• CLA has been signed and all committers have signed the CLA in this PR.

[codecov]

Codecov Report

Base: 0.02% // Head: 91.55% // Increases project coverage by +91.53% 🎉

Coverage data is based on head (bc75e88) compared to base (b8b31e9).
Patch coverage: 59.86% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff              @@
##           dev-1.x     #926       +/-   ##
============================================
+ Coverage     0.02%   91.55%   +91.53%     
============================================
  Files          121      129        +8     
  Lines         8217     9664     +1447     
  Branches      1368     1517      +149     
============================================
+ Hits             2     8848     +8846     
+ Misses        8215      626     -7589     
- Partials         0      190      +190     

Flag	Coverage Δ
unittests	91.55% <59.86%> (+91.53%)	⬆️

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

Impacted Files	Coverage Δ
mmcls/apis/inference.py	0.00% <0.00%> (ø)
mmcls/datasets/multi_label.py	100.00% <ø> (+100.00%)	⬆️
mmcls/models/backbones/edgenext.py	95.20% <ø> (ø)
mmcls/models/backbones/efficientformer.py	95.08% <ø> (ø)
mmcls/models/backbones/mobileone.py	94.47% <ø> (ø)
mmcls/models/backbones/mvit.py	92.46% <ø> (ø)
mmcls/models/backbones/repvgg.py	96.84% <ø> (+96.84%)	⬆️
mmcls/models/backbones/res2net.py	95.50% <ø> (+95.50%)	⬆️
mmcls/models/backbones/resnet.py	100.00% <ø> (+100.00%)	⬆️
mmcls/models/backbones/shufflenet_v1.py	97.91% <ø> (+97.91%)	⬆️
... and 141 more

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[okotaku]

@zzc98 @Ezra-Yu

Thank you for creating useful components!
I have other arcface implementation and I prefer it.
Please check it too.

#933

[okotaku]

LGTM

[Ezra-Yu]

LGTM.