Unify model initialization

[GT9505]

Refactoring model initialization methods based MMCV. For more information, please refer to open-mmlab/mmcv#780 and open-mmlab/mmdet#4750

[codecov]

Codecov Report

Merging #235 (9fb8ff3) into master (63db5ee) will decrease coverage by 1.06%.
The diff coverage is 46.36%.

❗ Current head 9fb8ff3 differs from pull request most recent head 4d89200. Consider uploading reports for the commit 4d89200 to get more accurate results

@@            Coverage Diff             @@
##           master     #235      +/-   ##
==========================================
- Coverage   69.62%   68.56%   -1.07%     
==========================================
  Files          87       87              
  Lines        4563     4542      -21     
  Branches      887      885       -2     
==========================================
- Hits         3177     3114      -63     
- Misses       1091     1146      +55     
+ Partials      295      282      -13     

Flag	Coverage Δ
unittests	68.53% <46.36%> (-1.07%)	⬇️

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

Impacted Files	Coverage Δ
mmtrack/apis/inference.py	12.37% <0.00%> (-0.13%)	⬇️
mmtrack/models/reid/base_reid.py	86.95% <ø> (-1.05%)	⬇️
mmtrack/models/mot/deep_sort.py	50.87% <14.28%> (-9.51%)	⬇️
mmtrack/models/mot/tracktor.py	57.35% <14.28%> (-8.28%)	⬇️
mmtrack/models/vid/dff.py	63.04% <16.66%> (-5.85%)	⬇️
mmtrack/models/vid/fgfa.py	61.90% <16.66%> (-4.23%)	⬇️
mmtrack/models/vid/selsa.py	66.03% <25.00%> (-1.56%)	⬇️
mmtrack/models/sot/siamrpn.py	81.42% <27.27%> (-7.63%)	⬇️
mmtrack/models/aggregators/embed_aggregator.py	100.00% <100.00%> (ø)
mmtrack/models/aggregators/selsa_aggregator.py	100.00% <100.00%> (ø)
... and 16 more

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