Mmdet scnet support

[ganesh3]

Added support for scnet

[codecov]

Codecov Report

Merging #921 (079b4bb) into master (b4a4148) will increase coverage by 0.05%.
The diff coverage is 95.45%.

@@            Coverage Diff             @@
##           master     #921      +/-   ##
==========================================
+ Coverage   85.71%   85.77%   +0.05%     
==========================================
  Files         255      258       +3     
  Lines        5658     5679      +21     
==========================================
+ Hits         4850     4871      +21     
  Misses        808      808              

Flag	Coverage Δ
unittests	85.77% <95.45%> (+0.05%)	⬆️

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

Impacted Files	Coverage Δ
icevision/core/components/composite.py	94.23% <ø> (ø)
icevision/data/dataset.py	96.66% <ø> (ø)
...ision/metrics/confusion_matrix/confusion_matrix.py	83.54% <ø> (ø)
icevision/models/base_show_results.py	100.00% <ø> (ø)
icevision/models/checkpoint.py	10.95% <ø> (ø)
icevision/models/fastai/unet/fastai/learner.py	100.00% <ø> (ø)
...sion/models/fastai/unet/lightning/model_adapter.py	41.37% <ø> (ø)
icevision/models/fastai/unet/prediction.py	96.87% <ø> (ø)
icevision/models/inference.py	75.38% <ø> (ø)
icevision/models/interpretation.py	100.00% <ø> (ø)
... and 16 more

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[FraPochetti]

@ai-fast-track shall we merge this one?