[Refactor] Unified parameter initialization

[dreamerlin]

Motivation

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

Dependency

open-mmlab/mmcv#780
open-mmlab/mmcv#884
open-mmlab/mmcv#893
open-mmlab/mmcv#899
open-mmlab/mmcv#902
open-mmlab/mmcv#918
open-mmlab/mmcv#930
open-mmlab/mmcv#959
open-mmlab/mmcv#971

Models

Action Recognition:

• TSN
• TSM
• TSM Non-Local
• R(2+1)D
• I3D
• SlowOnly
• SlowFast
• CSN
• TIN
• TPN
• C3D
• X3D
• OmniSource
• MultiModality: Audio
• TANet

Temporal Action Detection:

• BSN
• BMN
• SSN

Spatial Temporal Action Detection:

• SlowOnly+Fast R-CNN
• SlowFast+Fast R-CNN
• Long-Term Feature Bank

[codecov]

Codecov Report

Merging #794 (ba682e4) into master (6a252b8) will increase coverage by 0.00%.
The diff coverage is 83.48%.

❗ Current head ba682e4 differs from pull request most recent head 57474f9. Consider uploading reports for the commit 57474f9 to get more accurate results

@@           Coverage Diff           @@
##           master     #794   +/-   ##
=======================================
  Coverage   85.19%   85.20%           
=======================================
  Files         130      131    +1     
  Lines        9418     9415    -3     
  Branches     1591     1612   +21     
=======================================
- Hits         8024     8022    -2     
+ Misses        997      987   -10     
- Partials      397      406    +9     

Flag	Coverage Δ
unittests	85.20% <83.48%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
mmaction/models/__init__.py	100.00% <ø> (ø)
mmaction/datasets/base.py	59.71% <30.00%> (-1.01%)	⬇️
mmaction/datasets/builder.py	44.18% <33.33%> (+1.00%)	⬆️
mmaction/datasets/pipelines/loading.py	89.60% <50.00%> (-0.49%)	⬇️
mmaction/models/recognizers/recognizer2d.py	90.24% <75.00%> (ø)
mmaction/models/recognizers/recognizer3d.py	96.29% <75.00%> (ø)
mmaction/datasets/pipelines/augmentations.py	92.98% <78.94%> (-1.88%)	⬇️
mmaction/datasets/samplers/distributed_sampler.py	87.30% <84.21%> (+65.07%)	⬆️
mmaction/models/heads/trn_head.py	93.47% <93.47%> (ø)
mmaction/datasets/rawframe_dataset.py	96.66% <100.00%> (+8.60%)	⬆️
... and 35 more

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