Support number counting for flow-wise filename template

[irvingzhang0512]

Motivation

1. As inference_recognizer on optical flow model is throwing "FileNotFoundError, No such file or directory" accessing non existent frame on rawframe video #904 and the following comment shows, for now, in inference_recognizer we assumes files in video_path are all named with filename_tmpl. This pr removes the above restriction.

mmaction2/mmaction/apis/inference.py

Line 112 in f007661

# assuming files in ``video_path`` are all named with ``filename_tmpl`` # noqa: E501

2. We have already provided a way to fix bug in TSN temporal stream #565. However, we haven't modified related configs. So if we train flow models with default config, this shape mismatch bug still occurs.

Modification

1. For inference_recognizer, this pr count the file that filename format matches filename_impl, add some unittests.
2. For TSN Flow configs, this pr modifies in_channels of backbone

[codecov]

Codecov Report

Merging #922 (e60e6ab) into master (f007661) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #922      +/-   ##
==========================================
+ Coverage   83.58%   83.63%   +0.04%     
==========================================
  Files         132      132              
  Lines        9977     9983       +6     
  Branches     1720     1722       +2     
==========================================
+ Hits         8339     8349      +10     
+ Misses       1219     1218       -1     
+ Partials      419      416       -3     

Flag	Coverage Δ
unittests	83.63% <100.00%> (+0.04%)	⬆️

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Impacted Files	Coverage Δ
mmaction/apis/inference.py	89.85% <100.00%> (+8.90%)	⬆️
mmaction/datasets/pipelines/augmentations.py	91.95% <0.00%> (-0.81%)	⬇️
mmaction/datasets/pipelines/formating.py	92.00% <0.00%> (+4.00%)	⬆️

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[dreamerlin]

Thanks for your contribution for MMAction2!