[Feature] Add Maskfeat-1.x Support

[daidaiershidi]

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Motivation

Add maskfeat support.

Modification

Add MaskGenerator.
Add backbone of maskfeat.
Add head of maskfeat.
Add algorithms of maskfeat.
Add config of maskfeat.
Add Config of MaskFeat.

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)

If this PR introduces a new feature, it is better to list some use cases here and update the documentation.

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: 81.41% // Head: 82.16% // Increases project coverage by +0.74% 🎉

Coverage data is based on head (d1ea8b0) compared to base (3e3b315).
Patch coverage: 94.95% of modified lines in pull request are covered.

❗ Current head d1ea8b0 differs from pull request most recent head 797cf79. Consider uploading reports for the commit 797cf79 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x     #494      +/-   ##
===========================================
+ Coverage    81.41%   82.16%   +0.74%     
===========================================
  Files          113      118       +5     
  Lines         3961     4178     +217     
  Branches       563      605      +42     
===========================================
+ Hits          3225     3433     +208     
- Misses         627      631       +4     
- Partials       109      114       +5     

Flag	Coverage Δ
unittests	82.16% <94.95%> (+0.74%)	⬆️

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

Impacted Files	Coverage Δ
mmselfsup/datasets/transforms/wrappers.py	100.00% <ø> (ø)
mmselfsup/models/backbones/simmim_swin.py	86.95% <ø> (ø)
mmselfsup/models/heads/maskfeat_head.py	90.00% <90.00%> (ø)
mmselfsup/datasets/transforms/processing.py	89.76% <92.59%> (+0.32%)	⬆️
mmselfsup/models/utils/hog_layer.py	93.22% <93.22%> (ø)
mmselfsup/models/backbones/maskfeat_vit.py	97.61% <97.61%> (ø)
mmselfsup/datasets/transforms/__init__.py	100.00% <100.00%> (ø)
mmselfsup/models/algorithms/__init__.py	100.00% <100.00%> (ø)
mmselfsup/models/algorithms/maskfeat.py	100.00% <100.00%> (ø)
mmselfsup/models/backbones/__init__.py	100.00% <100.00%> (ø)
... and 7 more

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[tonysy]

LGTM