Fix for MMCLS1.x not being able to get classes information in checkpoint during inference

[kitecats]

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Motivation

Let MMCLS1.x get classes information from checkpoint during inference instead of using imagenet classes initialization

Modification

Please briefly describe what modification is made in this PR.

BC-breaking (Optional)

Does the modification introduce changes that break the backward compatibility of the downstream repositories?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

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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.

[CLAassistant]

All committers have signed the CLA.

[mzr1996]

LGTM, please sign the CLA before merge the PR.

[codecov]

Codecov Report

Base: 0.02% // Head: 91.57% // Increases project coverage by +91.55% 🎉

Coverage data is based on head (85dcf9a) compared to base (e8284a4).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##             1.x    #1093       +/-   ##
==========================================
+ Coverage   0.02%   91.57%   +91.55%     
==========================================
  Files        121      128        +7     
  Lines       8239     9603     +1364     
  Branches    1371     1508      +137     
==========================================
+ Hits           2     8794     +8792     
+ Misses      8237      624     -7613     
- Partials       0      185      +185     

Flag	Coverage Δ
unittests	91.57% <ø> (+91.55%)	⬆️

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/pipelines/processing.py
mmcls/data/__init__.py
mmcls/datasets/pipelines/__init__.py
mmcls/datasets/pipelines/formatting.py
mmcls/datasets/pipelines/compose.py
mmcls/data/cls_data_sample.py
mmcls/datasets/pipelines/auto_augment.py
mmcls/models/backbones/swin_transformer_v2.py	89.47% <0.00%> (ø)
mmcls/structures/cls_data_sample.py	100.00% <0.00%> (ø)
... and 124 more

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[mzr1996]

This PR will be merged to the dev-1.x branch and merged to the 1.x branch in the next release, thanks.