[Refactor] Use new API of matplotlib to handle blocking input in visualization.

[mzr1996]

Motivation

In matplotlib 3.5, the matplotlib.blocking_input module has been deprecated, which refers to this link.
Closing #566.

Modification

• As the title.
• And add a return value to BaseFigureContextManager.wait_continue() to indicate whether the user presses the continue key or closes the figure.
• In tools/visualizations/vis_pipeline.py, the progress will be interrupted if the user closes the show figure.

BC-breaking (Optional)

If users use the return value of ImshowInfosContextManager.put_img_infos, they need a small modification, from

img = manager.put_img_infos(img, {'info': 'text'})

to

_, img = manager.put_img_infos(img, {'info': 'text'})

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 #568 (84328e6) into master (00700d5) will decrease coverage by 0.05%.
The diff coverage is 90.47%.

@@            Coverage Diff             @@
##           master     #568      +/-   ##
==========================================
- Coverage   79.92%   79.86%   -0.06%     
==========================================
  Files         107      107              
  Lines        6102     6100       -2     
  Branches     1040     1042       +2     
==========================================
- Hits         4877     4872       -5     
- Misses       1093     1094       +1     
- Partials      132      134       +2     

Flag	Coverage Δ
unittests	79.86% <90.47%> (-0.06%)	⬇️

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

Impacted Files	Coverage Δ
mmcls/core/visualization/image.py	86.32% <90.47%> (-2.76%)	⬇️

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[Ezra-Yu]

LGTM.