[Refactor] Remove deprecation

[mzr1996]

Motivation

Several components have been deprecated for a long time. Remove them now.

Modification

1. Remove deprecated --options in some tools
2. Remove deprecated eval hooks and fp16 hooks
3. Remove deprecated mixup&cutmix and return_tuple arguments.
4. Remove deprecated deprecated_options in the multi-label dataset
5. Remove deprecated formating.py
6. Remove deprecated default mode of LabelSmoothLoss

BC-breaking (Optional)

These components or options have been deprecated for a long time, users should have stopped using them.

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

Merging #633 (c397926) into dev (a7f8e96) will increase coverage by 1.85%.
The diff coverage is 71.42%.

❗ Current head c397926 differs from pull request most recent head a9ec30e. Consider uploading reports for the commit a9ec30e to get more accurate results

@@            Coverage Diff             @@
##              dev     #633      +/-   ##
==========================================
+ Coverage   83.15%   85.01%   +1.85%     
==========================================
  Files         126      120       -6     
  Lines        7630     7362     -268     
  Branches     1332     1271      -61     
==========================================
- Hits         6345     6259      -86     
+ Misses       1095      915     -180     
+ Partials      190      188       -2     

Flag	Coverage Δ
unittests	85.01% <71.42%> (+1.85%)	⬆️

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

Impacted Files	Coverage Δ
mmcls/core/__init__.py	100.00% <ø> (ø)
mmcls/core/evaluation/__init__.py	100.00% <ø> (ø)
mmcls/datasets/multi_label.py	80.55% <ø> (+5.55%)	⬆️
mmcls/models/losses/label_smooth_loss.py	100.00% <ø> (ø)
mmcls/models/classifiers/image.py	91.30% <50.00%> (+6.42%)	⬆️
mmcls/apis/train.py	19.17% <100.00%> (-1.56%)	⬇️
mmcls/models/classifiers/base.py	76.31% <100.00%> (+1.92%)	⬆️

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[Ezra-Yu]

LGTM.